drm/msm/sde: check for null catalog in sde hw destroy

Fix sde hw deconstruction which can be called twice back to
back if hw initialization itself fails. In this case the catalog
pointer will already be null, so we must check for it.

Change-Id: Idc05efd7dd8c2a27f2c8128654e4c0b06697f39e
Signed-off-by: Lloyd Atkinson <latkinso@codeaurora.org>