drm/i915: Report if an unbannable context is involved in a GPU hang

Since unbannable contexts are special and supposed not to be causing GPU
hangs in the first place, make it clear when they are implicated in said
hang. In practice, most unbannable contexts are those created by igt
for the express purpose of throwing untold thousands of hangs at the GPU
and wish to keep doing so to finish the test. Normally they are cleaned
up, but it's when they or the other unbannable kernel contexts stay
stuck in an erroneous state that we need to worry and so need
highlighting.

Suggested-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180205094139.10671-1-chris@chris-wilson.co.uk


Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>