drm/i915: Allow error capture of a pending request

A hang situation has been observed where the only requests on the
context were either completed or not yet started according to the
breaadcrumbs. However, the register state claimed a batch was (maybe)
in progress. So, allow capture of the pending request on the grounds
that this might be better than nothing.

v2: Reword 'not started' warning message (Tvrtko)

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230127002842.3169194-6-John.C.Harrison@Intel.com