mmc: sdhci: disable pm qos voting when in cmdq mode

pm qos is currently causing race conditions with runtime pm when
in cmdq mode. Disable this till it is addressed as part of the
pm qos redesign.

Change-Id: I32d04100bbf31995a249188eace164c8761e9141
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>