drm/msm/a7xx: Call CP_RESET_CONTEXT_STATE

Calling this packet is necessary when we switch contexts because there
are various pieces of state used by userspace to synchronize between BR
and BV that are persistent across submits and we need to make sure that
they are in a "safe" state when switching contexts. Otherwise a
userspace submission in one context could cause another context to
function incorrectly and hang, effectively a denial of service (although
without leaking data). This was missed during initial a7xx bringup.

Fixes: af66706a ("drm/msm/a6xx: Add skeleton A7xx support")
Signed-off-by: Connor Abbott <cwabbott0@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/654924/


Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>