SGX-KM (hack): Workaround for kernel panic due to invalid sync objects

This fixes a problem when invalid syncobjects are accessed after the
swap chain has been destroyed. Should be reverted when final fix
is in place.

Change-Id: Iff4c23534e16f6a2ff86bfdf3a9c5dd33320e5cb
Author:    Kostiantyn Luzan <kostiantyn.luzan@ti.com>
Signed-off-by: Hemant Hariyani <hemanthariyani@ti.com>
Signed-off-by: Tate Hornbeck <tate.hornbeck@ti.com>