disp: msm: sde: add changes to fix get connector failure in rm_release

Currently during rm_release, drm_conn is available only if connector
and encoder are bound together. If a test_only commit occurs
before a non-blocking modeset commit, this bound is uncertain.
The resources allocated by test_only commit will not be released
and leads to resource allocation failures for the consequent
commits. Add changes to modify this by checking for the encoder
attached to sde_connector which happens during bootup.

Change-Id: Icb1d9595efda8a104ba527175b2dbc6a2c856d44
Signed-off-by: Jayaprakash <jmadiset@codeaurora.org>