msm: mdss: rotator: make work queue high priority

Janks in display are occurring due to delayed scheduling of rotator
work. Making it high priority would prevent such occurrences.

Change-Id: I85a7e4ca46596cfad56b29256ede30f1a13f0123
Signed-off-by: Terence Hampson <thampson@codeaurora.org>
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>