[Keyboard] Panc60 Refactor (#5559)

* remove unneeded uart setting

* use pragma once everywhere

* remove custom matrix support

* fixup readme

* set bootmagic to lite

* remove dependency on custom i2c code

* use the right header files and function calls

keyboards/panc60/panc60.c

@@ -24,7 +24,7 @@
 #include <avr/pgmspace.h>
 
 #include "action_layer.h"
-#include "i2c.h"
+#include "i2c_master.h"
 #include "quantum.h"
 
 __attribute__ ((weak))
@@ -44,7 +44,7 @@ void rgblight_set(void) {
     }
 
     i2c_init();
-    i2c_send(0xb0, (uint8_t*)led, 3 * RGBLED_NUM);
+    i2c_transmit(0xb0, (uint8_t*)led, 3 * RGBLED_NUM, 100);
 }
 #endif