UPSTREAM: mmc-utils: move offsetof from mmc.h to only user

offsetof isn't mmc specific, so remove it from mmc.h. As there is only a
single user define it there.

BUG=None
TEST=Compile

Signed-off-by: Uwe Kleine-Knig <u.kleine-koenig@pengutronix.de>
Signed-off-by: Chris Ball <chris@printf.net>
(cherry picked from commit a1a6120c34133d87bedfb04ab06ce43097c5e0d2)
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>

Change-Id: Iff5169b84d7981bff0e9ea2ba7ccc8476b6b69cf
Reviewed-on: https://chromium-review.googlesource.com/1114454
Commit-Ready: Gwendal Grignou <gwendal@chromium.org>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
2 files changed