disp: msm: sde: while timing engine enabling poll for active region

DCS commands triggered right after timing engine enable can conflict
with blanking period causing command transfer failures. Right after
timing engine enable poll for frame start and line count reaching
active region of display before any DCS commands.

Change-Id: Ia3967e01c3bb5bc82aa3549c300fa8335e00210c
Signed-off-by: Prabhanjan Kandula <quic_pkandula@quicinc.com>