[POWERPC] Fix warning on UP

arch/powerpc/platforms/pseries/pseries.h:24: warning: return type defaults to 'int'
arch/powerpc/platforms/pseries/pseries.h:25: warning: return type defaults to 'int'
arch/powerpc/platforms/pseries/pseries.h:24: warning: control reaches end of non-void function
arch/powerpc/platforms/pseries/pseries.h:25: warning: control reaches end of non-void function

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>