mmc: core: Core support for hs400 enhanced strobe

Add core support for hs400 enhanced strobe and flush
detect work as part of the mmc driver porting.

mmc: core: Fix voltage switching for ultra high speed card
Fix voltage switching for ultra high speed card.

Change-Id: Ie9e72c10b4beb06c59f0356c5258b8cfcb98d5b0
Signed-off-by: Ram Prakash Gupta <rampraka@codeaurora.org>