msm: kgsl: Correct snapshot over-write policy

Since non-gmu days, we have always kept the first gpu
snapshot around, until it was retrieved. Let's reinstate
that first i.e. never over-write existing snapshot with
a gpu fault.

Secondly, lets talk about gmu snapshot. if we want to
over-write a previously recovered fault with new gmu snapshot,
use the existing "prioritize_unrecoverable" sysfs knob.
By default, set it to false to mimic gpu fault policy of
keeping the first snapshot around.

Also, set the snapshot recovery bit as soon as we are past a
successful CP_INIT. This ensures that snapshot recovery bit is
set for a fault for which we didn't exercise dispatcher
based recovery.

Change-Id: Idae83344e3f70e451cd7cb036d6a0dcb76182172
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>