drm/msm/sde: avoid flagging autorefresh poll timeout

Autorefresh poll timeout may fail due to couple of
conditions like display continuous splash disabled
or autorefresh disable close to panel vsync. Avoid
flagging poll timeout error because these conditions
are recoverable.

Change-Id: I6adf6d29faeb72746c6bb2b4538902569b180164
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>