mmc: host: sdhci: allow definition of pm QoS via dts file

Add a new dts entry to define the CPU affinity in order to maintain
the IRQ pm_qos (Quality of Service) for targets that don't have little
cluster and allow setting the pm_qos to the little cluster,
to improve its performance.

Change-Id: Icf6125066d96331392d98a387974e54c96553306
Signed-off-by: Vince Leung <vincentl@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>