drivers/rtc: add support for Qualcomm PMIC8xxx RTC

Add support for PMIC8xxx based RTC.  PMIC8xxx is Qualcomm's power
management IC that internally houses an RTC module.  This driver
communicates with the PMIC module over SSBI bus.

[akpm@linux-foundation.org: cosmetic tweaks]
Acked-by: Wan ZongShun <mcuos.com@gmail.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>
Cc: Samuel Ortiz <sameo@linux.intel.com>
Cc: Wan ZongShun <mcuos.com@gmail.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>