drm/i915/tdr: Prepare error handler to accept mask of hung engines

In preparation for engine reset, the wedged argument of i915_handle_error()
is extended to reflect as a mask of engines that are hung. This is further
passed down to error state capture functions which are also updated.

Engine reset recovery mechanism uses this mask and schedules recovery work
for those particular engines.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Tomas Elf <tomas.elf@intel.com>
Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1458331676-567-3-git-send-email-arun.siluvery@linux.intel.com