UPSTREAM: mmc-utils: add ability to enable/disable optional eMMC cache

The MMC4.5 specification added an optional cache for eMMC devices.
This change will add the ability to enable/disable the cache.

Signed-off-by: Al Cooper <acooperx@gmail.com>
Signed-off-by: Chris Ball <chris@printf.net>
(cherry picked from commit d0b46442b50794217e53b2455c1344c548d9d088)
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>

BUG=none
TEST=Compiled, Installed on gnawty

Change-Id: I0d9e12abbd2b29bad564b869392ba2b0c51e246e
Reviewed-on: https://chromium-review.googlesource.com/338082
Commit-Ready: Gwendal Grignou <gwendal@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
4 files changed