m68k: atari: Add and use "atari.h"

When building with W=1:

    arch/m68k/atari/time.c:59:1: warning: no previous prototype for ‘atari_sched_init’ [-Wmissing-prototypes]
       59 | atari_sched_init(void)
	  | ^~~~~~~~~~~~~~~~
    arch/m68k/atari/time.c:140:5: warning: no previous prototype for ‘atari_mste_hwclk’ [-Wmissing-prototypes]
      140 | int atari_mste_hwclk( int op, struct rtc_time *t )
	  |     ^~~~~~~~~~~~~~~~
    arch/m68k/atari/time.c:199:5: warning: no previous prototype for ‘atari_tt_hwclk’ [-Wmissing-prototypes]
      199 | int atari_tt_hwclk( int op, struct rtc_time *t )
	  |     ^~~~~~~~~~~~~~
    arch/m68k/atari/ataints.c:267:13: warning: no previous prototype for ‘atari_init_IRQ’ [-Wmissing-prototypes]
      267 | void __init atari_init_IRQ(void)
	  |             ^~~~~~~~~~~~~~
    arch/m68k/atari/atasound.c:36:6: warning: no previous prototype for ‘atari_microwire_cmd’ [-Wmissing-prototypes]
       36 | void atari_microwire_cmd (int cmd)
	  |      ^~~~~~~~~~~~~~~~~~~
    arch/m68k/atari/atasound.c:53:6: warning: no previous prototype for ‘atari_mksound’ [-Wmissing-prototypes]
       53 | void atari_mksound (unsigned int hz, unsigned int ticks)
	  |      ^~~~~~~~~~~~~

Fix this by introducing a new header file "atari.h" for holding the
prototypes of functions implemented in arch/m68k/atari/.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/336e4a478ccbfd7e3e91cdbd27636947587a23a6.1694613528.git.geert@linux-m68k.org

arch/m68k/atari/ataints.c

@@ -52,6 +52,7 @@
 #include <asm/entry.h>
 #include <asm/io.h>
 
+#include "atari.h"
 
 /*
  * Atari interrupt handling scheme:
@@ -81,8 +82,6 @@ __ALIGN_STR "\n\t"
 	"orw	#0x200,%sp@\n\t"	/* set saved ipl to 2 */
 	"rte");
 
-extern void atari_microwire_cmd(int cmd);
-
 static unsigned int atari_irq_startup(struct irq_data *data)
 {
 	unsigned int irq = data->irq;

arch/m68k/atari/atari.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+
+struct rtc_time;
+
+/* ataints.c */
+void atari_init_IRQ(void);
+
+/* atasound.c */
+void atari_microwire_cmd(int cmd);
+void atari_mksound(unsigned int hz, unsigned int ticks);
+
+/* time.c */
+void atari_sched_init(void);
+int atari_mste_hwclk(int op, struct rtc_time *t);
+int atari_tt_hwclk(int op, struct rtc_time *t);

arch/m68k/atari/atasound.c

@@ -28,6 +28,7 @@
 #include <asm/irq.h>
 #include <asm/atariints.h>
 
+#include "atari.h"
 
 /*
  * stuff from the old atasound.c

arch/m68k/atari/config.c

@@ -48,6 +48,8 @@
 #include <asm/io.h>
 #include <asm/config.h>
 
+#include "atari.h"
+
 u_long atari_mch_cookie;
 EXPORT_SYMBOL(atari_mch_cookie);
 
@@ -69,19 +71,10 @@ int atari_rtc_year_offset;
 static void atari_reset(void);
 static void atari_get_model(char *model);
 static void atari_get_hardware_list(struct seq_file *m);
-
-/* atari specific irq functions */
-extern void atari_init_IRQ (void);
-extern void atari_mksound(unsigned int count, unsigned int ticks);
 #ifdef CONFIG_HEARTBEAT
 static void atari_heartbeat(int on);
 #endif
 
-/* atari specific timer functions (in time.c) */
-extern void atari_sched_init(void);
-extern int atari_mste_hwclk (int, struct rtc_time *);
-extern int atari_tt_hwclk (int, struct rtc_time *);
-
 /* ++roman: This is a more elaborate test for an SCC chip, since the plain
  * Medusa board generates DTACK at the SCC's standard addresses, but a SCC
  * board in the Medusa is possible. Also, the addresses where the ST_ESCC

arch/m68k/atari/time.c

@@ -23,6 +23,8 @@
 #include <asm/atariints.h>
 #include <asm/machdep.h>
 
+#include "atari.h"
+
 DEFINE_SPINLOCK(rtc_lock);
 EXPORT_SYMBOL_GPL(rtc_lock);