Some devices with a goodix touchscreen have more then 1 capacitive
touch-key. This commit replaces the current support for a single
touch-key, which ignored the reported key-code. With support for
up to 7 touch-keys, based upon checking the key-code which is
post-fixed to any reported touch-data.

KEY_LEFTMETA is assigned to the first touch-key (it will still be
the default keycode for devices with a single touch-key).
KEY_F1, KEY_F2... are assigned as default keycode for the other
touch-keys.

This commit also add supports for keycode remapping, so that
systemd-udev's hwdb can be used to remap the codes to send
keycodes to match the icons on the buttons for devices with more
then 1 touch-key.
Signed-off-by: Dmitry Mastykin <dmastykin@astralinux.ru>
Reviewed-by: Bastien Nocera <hadess@hadess.net>
Link: https://lore.kernel.org/r/20200316075302.3759-1-dmastykin@astralinux.ruSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>