rtc: add mxc driver for i.MX53 SRTC

rtc: add mxc driver for i.MX53 SRTC

Neither rtc-imxdi, rtc-mxc nor rtc-snvs are compatible with i.MX53.

This is driver enables support for the low power domain SRTC features:
- 32-bit MSB of non-rollover time counter
- 32-bit alarm register

Select the new config option RTC_DRV_MXC_V2 to build this driver

Based on:
http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/tree/drivers/rtc/rtc-mxc_v2.c?h=imx_2.6.35_11.09.01

Signed-off-by: Patrick Bruenn <p.bruenn@beckhoff.com>
Acked-by: Philippe Ombredanne <pombredanne@nexb.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>