msm: kgsl: Deregister gpu address on memdesc_sg_virt failure

When memdesc_sg_virt returns error in kgsl_setup_anon_useraddr function,
the gpu address registered in SVM region will not be deregistered.
This change deregisters the gpu address on memdesc_sg_virt failure.

Change-Id: Ic99167e283a0c6331bb9f5f0b608b6cdb3c918e4
Signed-off-by: Neeraja P <neerp@codeaurora.org>