msm: kgsl: Do not call dispatcher functions directly

With eCP, we will have a different dispatcher and hence a different
function to queue the commands to the eCP dispatcher. Instead of
adding the eCP check in kgsl.c, do it in adreno_queue_cmds. On the
same lines, we will do eCP check in adreno_drawctxt_sched() to queue
the context to the respective dispatcher. Also, move
adreno_drawctxt_sched() from adreno_drawctct.c to adreno.c so that we
have one less function to export.

Change-Id: Ibd6325131ed38b9527cdda084ca37d6c6ceee3bd
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>