ia64: don't do IA64_CMPXCHG_DEBUG without CONFIG_PRINTK

When CONFIG_PRINTK is not set, the CMPXCHG_BUGCHECK() macro calls
_printk(), but _printk() is a static inline function, not available
as an extern.
Since the purpose of the macro is to print the BUGCHECK info,
make this config option depend on PRINTK.

Fixes multiple occurrences of this build error:

../include/linux/printk.h:208:5: error: static declaration of '_printk' follows non-static declaration
  208 | int _printk(const char *s, ...)
      |     ^~~~~~~
In file included from ../arch/ia64/include/asm/cmpxchg.h:5,
../arch/ia64/include/uapi/asm/cmpxchg.h:146:28: note: previous declaration of '_printk' with type 'int(const char *, ...)'
  146 |                 extern int _printk(const char *fmt, ...);

Cc: linux-ia64@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Chris Down <chris@chrisdown.name>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>

arch/ia64/Kconfig.debug

@@ -39,7 +39,7 @@ config DISABLE_VHPT
 
 config IA64_DEBUG_CMPXCHG
 	bool "Turn on compare-and-exchange bug checking (slow!)"
-	depends on DEBUG_KERNEL
+	depends on DEBUG_KERNEL && PRINTK
 	help
 	  Selecting this option turns on bug checking for the IA-64
 	  compare-and-exchange instructions.  This is slow!  Itaniums