Input: charlieplex_keypad - add GPIO charlieplex keypad

Input: charlieplex_keypad - add GPIO charlieplex keypad

Add support for GPIO-based charlieplex keypad, allowing to control
N^2-N keys using N GPIO lines.

Reuse matrix keypad keymap to simplify, even if there is no concept
of rows and columns in this type of keyboard.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Link: https://patch.msgid.link/20260312180304.3865850-5-hugo@hugovil.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>