[Keyboard] Use old custom matrix for Drop Planck+Preonic (#14488)

Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: Jack Humbert <jack.humb@gmail.com>

keyboards/planck/rev6_drop/rules.mk

@@ -0,0 +1,33 @@
+# MCU name
+MCU = STM32F303
+
+# Bootloader selection
+BOOTLOADER = stm32-dfu
+
+# Build Options
+#   change yes to no to disable
+#
+BOOTMAGIC_ENABLE = yes      # Enable Bootmagic Lite
+MOUSEKEY_ENABLE = yes       # Mouse keys
+EXTRAKEY_ENABLE = yes       # Audio control and System control
+CONSOLE_ENABLE = yes        # Console for debug
+COMMAND_ENABLE = yes        # Commands for debug and configuration
+# Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
+SLEEP_LED_ENABLE = no       # Breathing sleep LED during USB suspend
+# if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
+NKRO_ENABLE = yes           # USB Nkey Rollover
+BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
+RGBLIGHT_ENABLE = yes       # Enable keyboard RGB underglow
+AUDIO_ENABLE = yes          # Audio output
+WS2812_DRIVER = pwm
+CUSTOM_MATRIX = yes
+# Do not enable RGB_MATRIX_ENABLE together with RGBLIGHT_ENABLE
+RGB_MATRIX_ENABLE = no
+RGB_MATRIX_DRIVER = WS2812
+ENCODER_ENABLE = yes
+DIP_SWITCH_ENABLE = yes
+
+SRC += matrix.c
+
+LAYOUTS = ortho_4x12 planck_mit
+LAYOUTS_HAS_RGB = no