UPSTREAM: GPU-DRM: Delete unnecessary checks before drm_property_unreference_blob()

UPSTREAM: GPU-DRM: Delete unnecessary checks before drm_property_unreference_blob()

The drm_property_unreference_blob() function tests whether its argument
is NULL and then returns immediately.
Thus the tests around the calls are not needed.

This issue was detected by using the Coccinelle software.

Link: http://patchwork.freedesktop.org/patch/msgid/563C8B3E.405@users.sourceforge.net
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit 5f911905054a64cf8c7871fddd33f4af74f07a17)

Change-Id: I599721227294c7cde5fd4f2ef6d5a97212b61b77
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Mark Yao <mark.yao@rock-chips.com>