msm: kgsl: Don't allocate memory for microcode if it is already allocated

This change adds a check to avoid allocating memory for loading microcode
in case it is already allocated. This avoids memory allocation failure
for microcode during multiple tries by userspace to open the kgsl device
in case of errors.

Change-Id: I018ebdb0dab1fc13af8d85a273c1c8b477fa1e26
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>