drmPrime*: initialize output args to 0

Fix Valgrind errors because those memory was uninitialized.

https://bugs.freedesktop.org/show_bug.cgi?id=90194
Signed-off-by: Guillaume Desmottes <guillaume.desmottes@collabora.co.uk>

v2: Explicitly zero the whole struct using memclear.
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
diff --git a/xf86drm.c b/xf86drm.c
index 0a66a4a..49da9c7 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -2721,6 +2721,8 @@
 	struct drm_prime_handle args;
 	int ret;
 
+	memclear(args);
+	args.fd = -1;
 	args.handle = handle;
 	args.flags = flags;
 	ret = drmIoctl(fd, DRM_IOCTL_PRIME_HANDLE_TO_FD, &args);
@@ -2736,8 +2738,8 @@
 	struct drm_prime_handle args;
 	int ret;
 
+	memclear(args);
 	args.fd = prime_fd;
-	args.flags = 0;
 	ret = drmIoctl(fd, DRM_IOCTL_PRIME_FD_TO_HANDLE, &args);
 	if (ret)
 		return ret;