msm: kgsl: Rename cmdbatch to drawobj

Rename all cmdbatch to drawobj. This forms a platform
for future changes where cmdbatch is split into different
types of drawobjs.

CRs-Fixed: 1054353
Change-Id: Ib84bee679e859db34e0d1f8a0ac70319eabddf53
Signed-off-by: Tarun Karra <tkarra@codeaurora.org>