drm/savage: clean up reclaim_buffers

drm/savage: clean up reclaim_buffers

The reclaim_buffers function of the savage driver actually wants to run
with the hw_lock held - at least there are printks in the call-chain
to that effect. But the drm core only calls reclaim_buffers as used
by savage _after_ forcefully dropping the hwlock (in case it's still
hold by the closing fd).

So do the same idlelock dance as for the other dma drivers and hope
that papers over any issues.

v2: Don't let the idlelock linger around.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Tormod Volden <debian.tormod@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>