Keyboard: Bpiphany Frosty Flake Refactor, Configurator support and readme cleanup (#4648)

* Frosty Flake: layout macro refactor

- frosty_flake.h updated to use #pragma once
- KEYMAP renamed to LAYOUT
- KEYMAP_TKL renamed to LAYOUT_tkl

* Frosty Flake: keymap refactor

- config.h files updated to #pragma once
- deleted deprecated build script rules from rules.mk
- keymap.c files:
  - #include QMK_KEYBOARD_H
  - updated layout macro name
  - white space changes for readability

* Frosty Flake: Configurator support

* Frosty Flake: readme cleanup

- Fixed Hardware Availability link (old link was 404)
- tiny grammar fix (colon missing on compile-and-flash instructions)

keyboards/bpiphany/frosty_flake/readme.md

@@ -18,7 +18,7 @@ keymaps `default` (104) and `tkl` (87) for example layouts.
 
 Keyboard Maintainer: QMK Community  
 Hardware Supported: Frosty Flake  
-Hardware Availability: https://1upkeyboards.com/qfr-frosty-flake-controller.html  
+Hardware Availability: [1upkeyboards](https://www.1upkeyboards.com/shop/controllers/qfr-frosty-flake-controller/)
 
 Make example for this keyboard (after setting up your build environment):
 
@@ -28,7 +28,7 @@ Make example for this keyboard (after setting up your build environment):
 make bpiphany/frosty_flake:default
 ```
 
-To directly flash the frosty_flake after compiling use
+To directly flash the frosty_flake after compiling use:
 
 ```
 make bpiphany/frosty_flake:default:dfu