drm/msm/sde: propagate error code for encoder atomic check

Encoder atomic check may fail while trying to reserve
the resources but error code was not propagated to calling
client. That leads to atomic commit without resource
reservation. Avoid such atomic commit by failing
atomic_check call.

Change-Id: I5ccd7813994d6cb72ef8866cc5a153ce8b3f9de4
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>