Move GMMK Pro layouts to the correct subdir (#14241)

Also fix a compilation issue in the mike1808 keymap

keyboards/gmmk/pro/ansi/keymaps/mike1808/encoder.h

@@ -0,0 +1,35 @@
+/* Copyright 2021 Mikael Manukyan <arm.localhost@gmail.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+// To add a new functionality define a new state here and then assign
+// the handler to the `encoder_callback`
+#include "quantum.h"
+
+enum encoder_state {
+    ENCODER_VOLUME = 0,
+    ENCODER_RGB_HUE,
+    ENCODER_RGB_SAT,
+    ENCODER_RGB_VAL,
+    ENCODER_RGB_EFFECT_SPEED,
+    ENCODER_RGB_EFFECT,
+};
+
+typedef void (*encoder_callback)(void);
+
+#define ENCODER_DEFAULT ENCODER_VOLUME
+
+void volume_up(void);
+void volume_down(void);