[Keyboard] Fix SRC include for matrix/m20add issi driver (#13826)

keyboards/matrix/m20add/rules.mk

@@ -25,5 +25,5 @@ RGBLIGHT_ENABLE = yes
 
 CUSTOM_MATRIX = lite
 # project specific files
-SRC += matrix.c tca6424.c rgb_ring.c issi/is31fl3731.c
+SRC += matrix.c tca6424.c rgb_ring.c drivers/led/issi/is31fl3731.c
 QUANTUM_LIB_SRC += i2c_master.c