msm: kgsl: Don't skip gmufw preallocations during firmware read

In scenario where GMU request firmware succeeded but preallocation
failed, a6xx_gmu_load_firmware returns error but during next open
call it return success only based on whether request_firmware was
successful or not. This results in issue during GMU start while
copying firmware to respective GMU memory blocks as some of the
memory blocks were not allocated.

Update the check in a6xx_gmu_load_firmware to ensure only request
firmware is skipped if it passed earlier.

Change-Id: I92920215aa9f47726c4470968ca804e1cee13468
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>
Signed-off-by: Pranav Patel <pranavp@codeaurora.org>