ANDROID: mmc: core: move to a SCHED_FIFO thread

(cherry picked from commit 011e507b413393eab8279dac8b778ad9b6e9971b)

Running mmcqd as a prio 120 thread forces it to compete with standard
user processes for IO performance, especially when the system is under
severe CPU load. Move it to a SCHED_FIFO thread to reduce the impact of
load on IO performance.

Signed-off-by: Tim Murray <timmurray@google.com>
Bug: 25392275
Change-Id: I1edfe73baa25e181367c30c1f40fee886e92b60d

[AmitP: Include <uapi/linux/sched/types.h> for struct sched_param]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>