disp: msm: sde: add traces for lastclose

Add logging during sde_kms_lastclose to know when driver cleanup
is being triggered. These traces are very helpful with debugging
shell stop/start issues.

Change-Id: I00ecc1287a3ee5cc096b7edc3f872e122b7d3fc8
Signed-off-by: Steve Cohen <cohens@codeaurora.org>