split_3x6_3 layout support (#9625)

keyboards/centromere/centromere.h

@@ -45,3 +45,5 @@
     { KC_NO, KC_NO, k32, k33, k34, k35, k36, k37, KC_NO, KC_NO }, \
     { KC_NO, KC_NO, k2a, k1a, k0a, k0b, k1b, k2b, KC_NO, KC_NO }  \
   }
+
+#define LAYOUT_split_3x6_3 LAYOUT

keyboards/centromere/rules.mk

@@ -40,3 +40,5 @@ OPT_DEFS += -DCENTROMERE_PROMICRO
 
 # # project specific files
 SRC = matrix.c
+
+LAYOUTS = split_3x6_3

keyboards/crkbd/rev1/rev1.h

@@ -52,3 +52,5 @@
                                             KC_##L30, KC_##L31, KC_##L32, KC_##R30, KC_##R31, KC_##R32 \
   )
 // clang-format on
+
+#define LAYOUT_split_3x6_3 LAYOUT

keyboards/crkbd/rev1/rules.mk

@@ -1,3 +1,5 @@
 SRC += 	matrix.c \
 		split_util.c \
 		split_scomm.c
+
+LAYOUTS = split_3x6_3