msm: kgsl: Update idle check for new GMU firmware

The new GMU firmware uses the same value to represent
the SPTPRAC PC and IFPC idle levels. If we are doing
IFPC, GX must be off for IFPC to be complete.
Update our idle check to take these criteria into account.
We must also check for idle before finishing adreno_stop().
Factor out this check and add it there as well.

CRs-Fixed: 2085877
Change-Id: Idd252aa4c91c640406907424dff39e2f9b6f5b6c
Signed-off-by: Kyle Piefer <kpiefer@codeaurora.org>