[Keyboard] Refactor HB85 to get rid of custom i2c code (#5570)

* remove dependency on custom i2c code

* missed a pragma once

* fix readme install instructions

* config.h cleanup

* make the bootmagic key not the same bmc reset key

* disable bootmagic functionality as it doesn't seem to work on atmega32a bmc boards

keyboards/gray_studio/hb85/usbconfig.h

@@ -8,8 +8,7 @@
  * This Revision: $Id: usbconfig-prototype.h 785 2010-05-30 17:57:07Z cs $
  */
 
-#ifndef __usbconfig_h_included__
-#define __usbconfig_h_included__
+#pragma once
 
 #include "config.h"
 
@@ -392,5 +391,3 @@ section at the end of this file).
 /* #define USB_INTR_PENDING        EIFR */
 #define USB_INTR_PENDING_BIT    INTF1
 #define USB_INTR_VECTOR         INT1_vect
-
-#endif /* __usbconfig_h_included__ */