msm: kgsl: Replace scm call api with its atomic version

scm_call2() API can block indefinitely if another client is using
this API. This is due to a mutex in this API to serialize calls to
the TZ. This blocks the GPU wake up which in turn can result in
kgsl fence timeouts. Since CPZ register programing is handled at
the hypervisor, we can safely avoid this serialization by using
scm_call2_atomic() API which doesn't block.

Change-Id: I48ba3e1a682e1027463a1c6b067e6cfcb4a0e8bc
Signed-off-by: Akhil P Oommen <akhilpo@codeaurora.org>