DRM_RDWR was not defined until libdrm 2.4.68. However,
in configure.ac we only require libdrm >= 2.4.55.
Seems silly to to bump minimum libdrm version for a simple
define. Thus, define DRM_RDWR if it's not defined.
This fixes compilation error introduced in:
commit 922031b0f98bf5c7b01f4431d1c08617f65865f7
Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Date: Tue Sep 12 12:07:13 2017 -0400
kms: Export DMABuf from Dumb buffer when possible
https://bugzilla.gnome.org/show_bug.cgi?id=787593
Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
ddba9e40f2