mmc: core: ignore cmdq halt failure when no change is needed

During system suspend CQE halted by queue suspend even before mmc host
suspend. When mmc host suspend calls halt helper, CQE is already halted.

This change ignores error value of halt helper.

Change-Id: I2d1456333f1d04f0e7a77485443b80a0ccaa3b4e
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>