powerpc/time: Fix sparse warnings

We found these warnings in arch/powerpc/kernel/time.c as follows:
  warning: symbol 'decrementer_max' was not declared. Should it be static?
  warning: symbol 'rtc_lock' was not declared. Should it be static?
  warning: symbol 'dtl_consumer' was not declared. Should it be static?

Declare 'decrementer_max' in powerpc asm/time.h.

Include linux/mc146818rtc.h in powerpc kernel/time.c where 'rtc_lock' is
declared. And remove duplicated declaration of 'rtc_lock' in powerpc
platforms/chrp/time.c because it has included linux/mc146818rtc.h.

Move 'dtl_consumer' definition after "include <asm/dtl.h>" because it is
declared there.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: He Ying <heying24@huawei.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210324090939.143477-1-heying24@huawei.com

arch/powerpc/include/asm/time.h

@@ -24,6 +24,7 @@ extern unsigned long tb_ticks_per_jiffy;
 extern unsigned long tb_ticks_per_usec;
 extern unsigned long tb_ticks_per_sec;
 extern struct clock_event_device decrementer_clockevent;
+extern u64 decrementer_max;
 
 
 extern void generic_calibrate_decr(void);

arch/powerpc/kernel/time.c

@@ -54,8 +54,9 @@
 #include <linux/of_clk.h>
 #include <linux/suspend.h>
 #include <linux/processor.h>
-#include <asm/trace.h>
+#include <linux/mc146818rtc.h>
 
+#include <asm/trace.h>
 #include <asm/interrupt.h>
 #include <asm/io.h>
 #include <asm/nvram.h>
@@ -156,10 +157,6 @@ bool tb_invalid;
 u64 __cputime_usec_factor;
 EXPORT_SYMBOL(__cputime_usec_factor);
 
-#ifdef CONFIG_PPC_SPLPAR
-void (*dtl_consumer)(struct dtl_entry *, u64);
-#endif
-
 static void calc_cputime_factors(void)
 {
 	struct div_result res;
@@ -185,6 +182,8 @@ static inline unsigned long read_spurr(unsigned long tb)
 
 #include <asm/dtl.h>
 
+void (*dtl_consumer)(struct dtl_entry *, u64);
+
 /*
  * Scan the dispatch trace log and count up the stolen time.
  * Should be called with interrupts disabled.

arch/powerpc/platforms/chrp/time.c

@@ -30,8 +30,6 @@
 
 #include <platforms/chrp/chrp.h>
 
-extern spinlock_t rtc_lock;
-
 #define NVRAM_AS0  0x74
 #define NVRAM_AS1  0x75
 #define NVRAM_DATA 0x77