I'll add more fancy logic to them soon, so everyone really has to use
them. Plus they already provide some nice additional debug
infrastructure on top of direct ww_mutex usage for the fences tracked
by dma_resv.

v2: Fix the lost _interruptible (Michael)
Acked-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Russell King <linux+etnaviv@armlinux.org.uk>
Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: etnaviv@lists.freedesktop.org
Cc: "Ruhl, Michael J" <michael.j.ruhl@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191214000927.1616384-1-daniel.vetter@ffwll.ch