rtc-cmos.c : Fix warning on PowerPC

The following warning is seen while compilation of PowerPC kernel:

 CC      drivers/rtc/rtc-cmos.o
drivers/rtc/rtc-cmos.c:697:2: warning: #warning Assuming 128 bytes
of RTC+NVRAM address space, not 64 bytes.

Fix it by adding defined(__powerpc__).
Signed-off-by: Srikanth Krishnakar <skrishna@mvista.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

drivers/rtc/rtc-cmos.c

@@ -687,7 +687,8 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
 #if	defined(CONFIG_ATARI)
 	address_space = 64;
 #elif defined(__i386__) || defined(__x86_64__) || defined(__arm__) \
-			|| defined(__sparc__) || defined(__mips__)
+			|| defined(__sparc__) || defined(__mips__) \
+			|| defined(__powerpc__)
 	address_space = 128;
 #else
 #warning Assuming 128 bytes of RTC+NVRAM address space, not 64 bytes.