drm/bridge: analogix_dp: possible condition with no effect (if == else)

fix below warning reported by coccicheck

./drivers/gpu/drm/bridge/analogix/analogix_dp_core.c:1414:6-8: WARNING:
possible condition with no effect (if == else)

Signed-off-by: Hariprasad Kelam <hariprasad.kelam@gmail.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190525175937.GA29368@hari-Inspiron-1545