[POWERPC] Fix Kconfig warning

Fix config warning related to select usage:

drivers/macintosh/Kconfig:117:warning: 'select' used by config symbol 'PMAC_APM_EMU' refers to undefined symbol 'SYS_SUPPORTS_APM_EMULATION'
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

arch/powerpc/Kconfig

@@ -118,6 +118,7 @@ config GENERIC_BUG
 	depends on BUG
 
 config SYS_SUPPORTS_APM_EMULATION
+	default y if PMAC_APM_EMU
 	bool
 
 config DEFAULT_UIMAGE

drivers/macintosh/Kconfig

@@ -113,7 +113,6 @@ config PMAC_SMU
 
 config PMAC_APM_EMU
 	tristate "APM emulation"
-	select SYS_SUPPORTS_APM_EMULATION
 	select APM_EMULATION
 	depends on ADB_PMU && PM