Revert "mmc: core: Add 1ms delay after sending CMD6 to MMC cards."

This reverts commit def5e24abe4787b22b22138623eeb495ef8fec0d.

Reverted commit was added 3 years back due to this reason:
Some eMMC cards (SanDisk iNand eMMC cards to be specific) needed
this additional delay of 1 ms after sending the switch command to
card. This is a result of some issue with the SanDisk cards itself
and apparently they were going to fix this in their ASIC within
year or so. And Since Sandisk is one of the big players in the
eMMC space, it was important that our software works fine with their
cards.

But now we don't see any need of this additional delay on any of the
latest eMMC chipsets. Even open source version of this file doesn't
have this delay.

Change-Id: Iad5baa897f8fc0a360a17944fb87eb8e21e9bc53
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>