mmc: core: enable eMMC5.0 card detection

eMMC5.0 cards have become reality and Linux kernel shouldn't
shy away in supporting them :). This patch enables the eMMC5.0
card support on Linux.

Change-Id: I8fd3f52ed1706ad86bc0c049a004db3ee12184ff
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>