drm/via: copy DRM_WAIT_ON as VIA_WAIT_ON and use it

VIA_WAIT_ON() is a direct copy of DRM_WAIT_ON() from
drm_os_linux.h.
The copy is made so we can avoid the dependency on the legacy header.
A more involved approach had been to introduce wait_event_* but for this
legacy driver the simpler and more safe approach with a copy of the
macro was selected.
Added the relevant header files for the functions used in VIA_WAIT_ON.

v3:
- Updated users of DRM_WAIT_ON => VIA_WAIT_ON (Emil)
- Updated $subject (Emil)

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Cc: Kevin Brace <kevinbrace@gmx.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: Mike Marshall <hubcap@omnibond.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Michel Dänzer <michel@daenzer.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190723200944.17285-3-sam@ravnborg.org

drivers/gpu/drm/via/via_irq.c

@@ -233,12 +233,12 @@ via_driver_irq_wait(struct drm_device *dev, unsigned int irq, int force_sequence
 	cur_irq = dev_priv->via_irqs + real_irq;
 
 	if (masks[real_irq][2] && !force_sequence) {
-		DRM_WAIT_ON(ret, cur_irq->irq_queue, 3 * HZ,
+		VIA_WAIT_ON(ret, cur_irq->irq_queue, 3 * HZ,
 			    ((via_read(dev_priv, masks[irq][2]) & masks[irq][3]) ==
 			     masks[irq][4]));
 		cur_irq_sequence = atomic_read(&cur_irq->irq_received);
 	} else {
-		DRM_WAIT_ON(ret, cur_irq->irq_queue, 3 * HZ,
+		VIA_WAIT_ON(ret, cur_irq->irq_queue, 3 * HZ,
 			    (((cur_irq_sequence =
 			       atomic_read(&cur_irq->irq_received)) -
 			      *sequence) <= (1 << 23)));