msm: kgsl: Fix GPU hang recovery logic

During new commands submission, if the write pointer
is ahead of read pointer fill ringbuffer data with
KGSL_NOP_DATA_FILLER after NOP command. This will
avoids getting incorrect context ID from the ringbuffer
extraction logic during GPU recovery.

CRs-Fixed: 620533
Change-Id: If4d25770b7288bc6fb618611c150e3876cc87c6f
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>
msm: kgsl: Reset VSC control registers

Configure the A2xx VSC register in context switch,
which helps GPU to recover from the bad state.

CRs-Fixed: 637288
Change-Id: I2000a579614c491a015c618a52808500541329c5
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>