COMPMID-3981: Fix missing fallback for export to cl_image

COMPMID-3981: Fix missing fallback for export to cl_image

- Fix missing fallback in the CLGEMMReshaped heuristic on Mali-G77

Change-Id: I0a243c7ed153216966d0809a3b3348f030a845eb
Signed-off-by: Gian Marco Iodice <gianmarco.iodice@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/4463
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
(cherry picked from commit 8b84aaa4db093ac08efa96c2cbf766e800465529)
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/4162
Reviewed-by: SiCong Li <sicong.li@arm.com>