[ARM] rtc-pcf8583: Final fixes for this RTC on RiscPC

Replace the I2C bus address, as per drivers/acorn/char/pcf8583.c.

Also, since this driver also contains Acorn RiscPC specific code
for obtaining the current year from the SRAM (and updating the
platform specific checksum when writing new data back) this is
NOT a platform independent driver.

Document it as such, and update the dependencies to reflect this
fact.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/rtc/Kconfig

@@ -207,10 +207,12 @@ config RTC_DRV_PCF8563
 
 config RTC_DRV_PCF8583
 	tristate "Philips PCF8583"
-	depends on RTC_CLASS && I2C
+	depends on RTC_CLASS && I2C && ARCH_RPC
 	help
-	  If you say yes here you get support for the
-	  Philips PCF8583 RTC chip.
+	  If you say yes here you get support for the Philips PCF8583
+	  RTC chip found on Acorn RiscPCs.  This driver supports the
+	  platform specific method of retrieving the current year from
+	  the RTC's SRAM.
 
 	  This driver can also be built as a module. If so, the module
 	  will be called rtc-pcf8583.

drivers/rtc/rtc-pcf8583.c

@@ -40,7 +40,7 @@ struct pcf8583 {
 #define CTRL_ALARM	0x02
 #define CTRL_TIMER	0x01
 
-static unsigned short normal_i2c[] = { I2C_CLIENT_END };
+static unsigned short normal_i2c[] = { 0x50, I2C_CLIENT_END };
 
 /* Module parameters */
 I2C_CLIENT_INSMOD;