soc: qcom: hgsl: Add doorbell support to gvm

Used under guest system, it submits GPU tasks into hardware while host
driver is unaware of it.

Hgsl communicates with GPU hardware using either GPU registers or
TCSR compute signaling hardware block.

Change-Id: I881941953ee2340a4c47f10e85e4b0a1dfb87a50
Signed-off-by: Kasin Li <donglil@codeaurora.org>
Signed-off-by: Hai Li <hali@codeaurora.org>
Signed-off-by: Thomas (Wonyoung) Yun <wyun@codeaurora.org>