drm/msm/shd: fix missing return value

Check to validate return value of drm_atomic_set_mode_for_crtc
and print the error log if non-zero value is returned which
indicates failure.

Change-Id: I6a21b9ec64e9140b314dc52a34c6be8b385c6584
Signed-off-by: Rahul Sharma <rahsha@codeaurora.org>