mmc: Allow forward compatibility for eMMC

As stated by the eMMC 5.0 specification, a chip should not be rejected
only because of the revision stated in the EXT_CSD_REV field of the
EXT_CSD register.

Remove the control on this value, the control of the CSD_STRUCTURE field
should be sufficient to reject future incompatible changes.

Change-Id: I655a59004e7e4997c12077d3a267e71344f10b66
Signed-off-by: Romain Izard <romain.izard.pro@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Git-commit: 03a59437ef6b6ad7fb0165cb9b96c08d6bf057fc
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>