powerpc/ps3: Fix build error on UP

A non-SMP version of smp_send_stop() is now included in smp.h.
Remove the unneeded definition in the PS3 smp.c.

Fixes build errors like these when CONFIG_SMP=n:

arch/powerpc/platforms/ps3/setup.c:49: error: redefinition of 'smp_send_stop'
include/linux/smp.h:125: error: previous definition of 'smp_send_stop' was here

Reported-by: Subrata Modak <[e-mail]>
Signed-off-by: Geoff Levand <[e-mail]>
Signed-off-by: Paul Mackerras <[e-mail]>

arch/powerpc/platforms/ps3/setup.c

···
 DEFINE_MUTEX(ps3_gpu_mutex);
 EXPORT_SYMBOL_GPL(ps3_gpu_mutex);
 
-#if !defined(CONFIG_SMP)
-static void smp_send_stop(void) {}
-#endif
-
 static union ps3_firmware_version ps3_firmware_version;
 
 void ps3_get_firmware_version(union ps3_firmware_version *v)