mmc: msm_sdcc: Add eMMCv4.5 BKOPS feature support

The change sets these bits in caps2 field of host controller:
1. MMC_CAP2_BKOPS - enables msm_sdcc host support for BKOPS.
2. MMC_CAP2_INIT_BKOPS - will set the BKOPS_EN bit in card
   ext_csd register. The bit is one time programmable.

Change-Id: Ic74e025469efdfaaec6d6fe6dc8bacc60462724d
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>