GPU-DRM: Delete unnecessary checks before drm_property_unreference_blob()

GPU-DRM: Delete unnecessary checks before drm_property_unreference_blob()

BugLink: http://bugs.launchpad.net/bugs/1599109
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.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
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)
Signed-off-by: Timo Aaltonen <timo.aaltonen@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>