drm: Change deadlock-avoidance algorithm for the modeset locks.

For modeset locks we don't expect a high number of contending
transactions so change algorithm from Wait-Die to Wound-Wait.

Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Acked-by: Ingo Molnar <mingo@kernel.org>