rtc: add driver for MXC's internal RTC module

This adds a driver for Freescale's MXC internal real time clock modules.

The code is taken from Freescale's BSPs, but modified to fit the current
kernel coding mechanisms.  Also, the PMIC external clock function was
removed for now to not add dead bits and keep the code as simple as
possible.

[akpm@linux-foundation.org: make PIE_BIT_DEF[] static]
Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Alessandro Zummo <a.zummo@towertech.it>

Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Daniel Mack <daniel@caiaq.de>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>