[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/rules.mk

@@ -31,7 +31,7 @@ F_CPU = 12000000
 BOOTLOADER = bootloadHID
 
 # build options
-BOOTMAGIC_ENABLE = yes
+BOOTMAGIC_ENABLE = lite
 MOUSEKEY_ENABLE = yes
 EXTRAKEY_ENABLE = yes
 CONSOLE_ENABLE = yes
@@ -43,8 +43,7 @@ RGBLIGHT_CUSTOM_DRIVER = yes
 OPT_DEFS = -DDEBUG_LEVEL=0
 
 # custom matrix setup
-CUSTOM_MATRIX = yes
-SRC = matrix.c i2c.c
+SRC = i2c_master.c
 
 # programming options
 PROGRAM_CMD = ./util/atmega32a_program.py $(TARGET).hex