refactor: move default RGB/LED matrix #defines (#21938)

* refactor: move default RGB/LED matrix #defines

Moving the fallback definitions of macros like LED_MATRIX_VAL_STEP and
RGB_MATRIX_MAXIMUM_BRIGHTNESS to header files allows keyboards to
leverage these defaults without requiring #ifdef guards (and often
repeating said fallback definitions).

* style: use if(n)def for consistency

and remove redundant UINT8_MAX checks on maximum brightness

Co-authored-by: Joel Challis <git@zvecr.com>

* refactor: remove INDICATOR_MAX_BRIGHTNESS macro

Co-authored-by: Joel Challis <git@zvecr.com>

---------

Co-authored-by: Joel Challis <git@zvecr.com>

keyboards/kbdfans/kbd67/mkiirgb/v3/info.json

@@ -5,7 +5,8 @@
         "device_version": "0.0.3"
     },
     "rgb_matrix": {
-        "driver": "is31fl3741"
+        "driver": "is31fl3741",
+        "val_steps": 8
     },
     "matrix_pins": {
         "cols": ["F7", "F6", "F5", "C7", "B0", "B1", "B2", "B3", "B4", "D7", "D6", "D4", "D5", "D3", "D2"],

keyboards/kbdfans/kbd67/mkiirgb/v3/v3.c

@@ -125,16 +125,12 @@ led_config_t g_led_config = { {
 
 #if defined(RGB_MATRIX_ENABLE) && defined(CAPS_LOCK_LED_INDEX)
 
-#ifdef RGB_MATRIX_MAXIMUM_BRIGHTNESS
+#if !defined(CAPS_LOCK_MAX_BRIGHTNESS)
     #define CAPS_LOCK_MAX_BRIGHTNESS RGB_MATRIX_MAXIMUM_BRIGHTNESS
-#else
-    #define CAPS_LOCK_MAX_BRIGHTNESS 0xFF
 #endif
 
-#ifdef RGB_MATRIX_VAL_STEP
+#if !defined(CAPS_LOCK_VAL_STEP)
     #define CAPS_LOCK_VAL_STEP RGB_MATRIX_VAL_STEP
-#else
-    #define CAPS_LOCK_VAL_STEP 8
 #endif
 
 bool rgb_matrix_indicators_kb(void) {