mmc: sdhci: add post halt helper to support command queue hosts

After halting the CQE, an unexpected legacy irq may be received by the
controller. The post halt helper function acknowledges this irq and
handles it.

Change-Id: Iaaa4e57fba830d626fad693ff33dd966994bc50f
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>