compositor-drm: Zero drmModeAddFB2 data

Initialize arrays of data passed to drmModeAddFB2, just as
drm_fb_get_from_bo does.

See https://lists.freedesktop.org/archives/wayland-devel/2016-August/030645.html

Signed-off-by: Yong Bakos <ybakos@humanoriented.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>

libweston/compositor-drm.c

@@ -319,7 +319,7 @@ drm_fb_create_dumb(struct drm_backend *b, unsigned width, unsigned height,
 	ret = -1;
 
 	if (!b->no_addfb2) {
-		uint32_t handles[4], pitches[4], offsets[4];
+		uint32_t handles[4] = { 0 }, pitches[4] = { 0 }, offsets[4] = { 0 };
 
 		handles[0] = fb->handle;
 		pitches[0] = fb->stride;