ARM: mmp: enable rtc in pxa910

Support rtc-sa1100 driver in pxa910.

Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
diff --git a/arch/arm/mach-mmp/include/mach/regs-apbc.h b/arch/arm/mach-mmp/include/mach/regs-apbc.h
index 1a96585..8a37fb0 100644
--- a/arch/arm/mach-mmp/include/mach/regs-apbc.h
+++ b/arch/arm/mach-mmp/include/mach/regs-apbc.h
@@ -57,6 +57,7 @@
 #define APBC_PXA910_SSP1	APBC_REG(0x01c)
 #define APBC_PXA910_SSP2	APBC_REG(0x020)
 #define APBC_PXA910_IPC		APBC_REG(0x024)
+#define APBC_PXA910_RTC		APBC_REG(0x028)
 #define APBC_PXA910_TWSI0	APBC_REG(0x02c)
 #define APBC_PXA910_KPC		APBC_REG(0x030)
 #define APBC_PXA910_TIMERS	APBC_REG(0x034)