drm/arm/mali-dp: Add a loop around the second set CVAL and try 5 times

This patch trying to fix monitor freeze issue caused by drm error
'flip_done timed out' on LS1028A platform. this set try is make a loop
around the second setting CVAL and try like 5 times before giveing up.

Signed-off-by: Wen He <wen.he_1@nxp.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>