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/winkeyless/bmini/bmini.c

@@ -16,6 +16,3 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
 #include "bmini.h"
-
-__attribute__ ((weak))
-void matrix_scan_user(void) {}