st/glx: consolidate C sources list into Makefile.sources

Move glx/{,xlib/}Makefile.am to preserve file list

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Tom Stellard <thomas.stellard@amd.com>
diff --git a/configure.ac b/configure.ac
index 8ccbc28..e7c8223 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2025,7 +2025,7 @@
 		src/gallium/state_trackers/dri/sw/Makefile
 		src/gallium/state_trackers/egl/Makefile
 		src/gallium/state_trackers/gbm/Makefile
-		src/gallium/state_trackers/glx/Makefile
+		src/gallium/state_trackers/glx/xlib/Makefile
 		src/gallium/state_trackers/osmesa/Makefile
 		src/gallium/state_trackers/vdpau/Makefile
 		src/gallium/state_trackers/vega/Makefile