Do not hard set config in CPTC files (#11864)

common_features.mk

@@ -350,7 +350,11 @@ endif
 VALID_BACKLIGHT_TYPES := pwm timer software custom
 
 BACKLIGHT_ENABLE ?= no
-BACKLIGHT_DRIVER ?= pwm
+ifeq ($(strip $(CONVERT_TO_PROTON_C)), yes)
+    BACKLIGHT_DRIVER ?= software
+else
+    BACKLIGHT_DRIVER ?= pwm
+endif
 ifeq ($(strip $(BACKLIGHT_ENABLE)), yes)
     ifeq ($(filter $(BACKLIGHT_DRIVER),$(VALID_BACKLIGHT_TYPES)),)
         $(error BACKLIGHT_DRIVER="$(BACKLIGHT_DRIVER)" is not a valid backlight type)

platforms/chibios/QMK_PROTON_C/convert_to_proton_c.mk

@@ -5,8 +5,5 @@ BOARD := QMK_PROTON_C
 OPT_DEFS += -DCONVERT_TO_PROTON_C
 
 # These are defaults based on what has been implemented for ARM boards
-AUDIO_ENABLE = yes
-WS2812_DRIVER = bitbang
-
-# Force task driven PWM until ARM can provide automatic configuration
-BACKLIGHT_DRIVER = software
+AUDIO_ENABLE ?= yes
+WS2812_DRIVER ?= bitbang