disp: msm: assign aspace to gem object for mmap buffer

During gem fault, if aspace value is found to be NULL
pages map request will be failed. This change assigns
nonsecure aspace to gem object before mapping the pages
in such cases.

Change-Id: Ia838fd8a446e21771742ec9d51e30fe08c989e6e
Signed-off-by: Yashwanth <yvulapu@codeaurora.org>