[POWERPC] PS3: Use __maybe_unused

Change the PS3 debug routines from using the GCC specific
'__attribute__ ((unused))' to the preprocessor macro
__maybe_unused.

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/ps3/time.c

@@ -39,7 +39,7 @@ static void _dump_tm(const struct rtc_time *tm, const char* func, int line)
 }
 
 #define dump_time(_a) _dump_time(_a, __func__, __LINE__)
-static void __attribute__ ((unused)) _dump_time(int time, const char* func,
+static void __maybe_unused _dump_time(int time, const char *func,
 	int line)
 {
 	struct rtc_time tm;