input: twl4030: Keypad scan and input

This allows scanning the twl4030 keypad, storing the result in a 64-byte long
matrix with the twl4030_keypad_scan function.

Detecting a key at a given column and row is made easier with the
twl4030_keypad_key function.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-by: Tom Rini <trini@konsulko.com>

include/twl4030.h

@@ -683,6 +683,9 @@ int twl4030_input_power_button(void);
 int twl4030_input_charger(void);
 int twl4030_input_usb(void);
 
+int twl4030_keypad_scan(unsigned char *matrix);
+int twl4030_keypad_key(unsigned char *matrix, u8 c, u8 r);
+
 /*
  * LED
  */