rtc: Add MCP79411 support to DS1307 rtc driver

The code is from Adrian Cox, and is patterned after similar
support in Linux (drivers/rtc/rtc-ds1307.c:1121-1135). This
chip is used on the Cyrus board from Varisys.

Signed-off-by: Andy Fleming <afleming@gmail.com>
Reviewed-by: York Sun <yorksun@freescale.com>