msm_fb: quickdraw: schedule work to free buffer fds

The buffer file descriptors are allocated in a kworker thread, so they
are only valid in kworker threads. Previously, the buffer file descriptors
were freed from a user space process. This left a dangling file descriptor
in the kworker thread which was never freed.

Change-Id: Ifad691d912f5d37962c0854bf3d2c32e3258e553
Signed-off-by: Fred Fettinger <fred.fettinger@motorola.com>
Reviewed-on: http://gerrit.pcs.mot.com/603536
Tested-by: Jira Key <jirakey@motorola.com>
Reviewed-by: Joseph Swantek <jswantek@motorola.com>
Reviewed-by: Patrick Auchter <auchter@motorola.com>
SLTApproved: Maulik Desai <amd093@motorola.com>
Submit-Approved: Maulik Desai <amd093@motorola.com>
Reviewed-by: Jared Suttles <jsuttles@motorola.com>
Reviewed-by: Zachary Crosby <zac@motorola.com>
Reviewed-by: Fred Fettinger <fettinge@motorola.com>
Reviewed-by: Russell Knize <rknize@motorola.com>
(cherry picked from commit 63463ba519b86ccef5c727e990c244a54ed45df6)
Reviewed-on: http://gerrit.pcs.mot.com/603807
Reviewed-by: Maulik Desai <amd093@motorola.com>
Tested-by: Maulik Desai <amd093@motorola.com>