UPSTREAM: mmc: core: Update the ext-csd.rev check for eMMC5.1

With the new eMMC5.1 spec, there is a new EXT_CSD register with
the revision number(EXT_CSD_REV) 7. This patch updates the check
for ext-csd.rev number as 7.

Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd@samsung.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Chris Ball <cjb@laptop.org>
(cherry picked from commit 6636bad839d9936e73e48c4841eda83a58fcdb53)
Signed-off-by: Benson Leung <bleung@chromium.org>

BUG=chrome-os-partner:29768
TEST=Builds clean.

Change-Id: I28be28bde631b6569b6cb2c3a1778557f565d71a
Reviewed-on: https://chromium-review.googlesource.com/181065
Reviewed-by: Puthikorn Voravootivat <puthik@chromium.org>
Commit-Queue: Benson Leung <bleung@chromium.org>
Tested-by: Benson Leung <bleung@chromium.org>
(cherry picked from commit 07e1a9b475c46a0af5db4ba18251a8f6e4b8c072)
Reviewed-on: https://chromium-review.googlesource.com/207182
Reviewed-by: Benson Leung <bleung@chromium.org>
Commit-Queue: Gwendal Grignou <gwendal@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>