drm/radeon/kms: use udelay for short delays

commit 01d45039 upstream.

For usec delays use udelay instead of scheduling, this should
allow reclocking to happen faster. This also was the cause
of reported 33s delays at bootup on certain systems.

fixes: freedesktop.org bug 25506
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/gpu/drm/radeon/atom.c

@@ -607,7 +607,7 @@ static void atom_op_delay(atom_exec_context *ctx, int *ptr, int arg)
 	uint8_t count = U8((*ptr)++);
 	SDEBUG("   count: %d\n", count);
 	if (arg == ATOM_UNIT_MICROSEC)
-		schedule_timeout_uninterruptible(usecs_to_jiffies(count));
+		udelay(count);
 	else
 		schedule_timeout_uninterruptible(msecs_to_jiffies(count));
 }