[POWERPC] Fix drivers/rtc/Kconfig for powerpc

The powerpc arch uses CONFIG_PPC instead of CONFIG_POWERPC.  This fixes
drivers/rtc/Kconfig to use the correct config option.
Signed-off-by: NWade Farnsworth <wfarnsworth@mvista.com>
Acked-by: NJon Loeliger <jdl@freescale.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

drivers/rtc/Kconfig

@@ -246,7 +246,7 @@ comment "Platform RTC drivers"
 config RTC_DRV_CMOS
 	tristate "PC-style 'CMOS'"
 	depends on RTC_CLASS && (X86 || ALPHA || ARM26 || ARM \
-		|| M32R || ATARI || POWERPC || MIPS)
+		|| M32R || ATARI || PPC || MIPS)
 	help
 	  Say "yes" here to get direct support for the real time clock
 	  found in every PC or ACPI-based system, and some other boards.