mmc: msm_sdcc: Advertise erase capability

SD/MMC card erase functionality is available in core
layer. Enable MMC_CAP_ERASE capability from host side
so that users can use erase, trim, secure erase, secure trim
operations based on the card capability.

Change-Id: Icf35cd3038b0a95d653387d42870357c4c3853c0
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>