Initial commit for Planck PCB Rev 1.

- Backlight on PB7 controlled by Timer1 Fast PWM (no interrupts).
- Backlight commands connected temporarily to top left keys.
- Backlight init called from matrix.c, since there's no generic keyboard_init() override function.

keyboard/planck/config.h

@@ -34,6 +34,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 /* define if matrix has ghost */
 //#define MATRIX_HAS_GHOST
 
+/* number of backlight levels */
+/* NOTE: this is the max value of 0..BACKLIGHT_LEVELS so really 16 levels. */
+#define BACKLIGHT_LEVELS 15
+
 /* Set 0 if debouncing isn't needed */
 #define DEBOUNCE    5