swr: call swr_update_derived unconditionally when drawing/clearing

swr: call swr_update_derived unconditionally when drawing/clearing

Currently a sequence like draw/map/draw/map will cause the second map to
not wait for the second draw. This is because the first map will clear
the resource business bit, and the second draw won't reset it since no
state has changed.

swr_update_derived does a tiny bit of extra work, including updating the
SWR_BACKEND_STATE as well as waiting for prending fences. If that's a
problem, we could call swr_update_resource_status directly from
draw/clear handlers.

Fixes clearbuffer-stencil, clearbuffer-depth, clearbuffer-depth-stencil,
and clearbuffer-display-lists.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Bruce Cherniak <bruce.cherniak@intel.com>