msm: kgsl: Remove A4XX references from ringbuffer_submitcmd()

adreno_ringbuffer_submitcmd() is a neutral function and should not
use specific GPU family registers and functions. Replace all A4XX
references with generic adreno functions and registers.

Change-Id: Ifc2b2ceaaeb5f3e05d20efb43f542b858225b829
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>