Remove custom matrix from PS2AVRGB boards (#7396)

* Remove custom matrix from PS2AVRGB boards

* Add custom backlight.c to SRC for bminiex, for now

* Add missing DIODE_DIRECTIONs

keyboards/coseyfannitutti/discipad/discipad.c

@@ -14,11 +14,3 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 #include "discipad.h"
-
-
-void matrix_init_kb(void) {
-	// put your keyboard start-up code here
-	// runs once when the firmware starts up
-
-	matrix_init_user();
-}