disp: msm: sde: fix error return in plane atomic_check

In plane atomic_check function, the error code
from one of the checks is overwritten by the
return-value of subsequent check. This leads to
wrong return-value propagation resulting in
undefined behavior. Fix it to return the appropriate
error code on any failure.

Change-Id: I53b427d1b69c3ebfaa6709814bd9095676ff942d
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>