Input: edt-ft5x06 - add support for regulator

Add the support for enabling optional regulator that may be used as VCC
source.

Signed-off-by: Mylène Josserand <mylene.josserand@bootlin.com>
Signed-off-by: Ondrej Jirman <megous@megous.com>
Reviewed-by: Rob Herring <robh@kernel.org> # bindings
Link: https://lore.kernel.org/r/20191029005806.3577376-2-megous@megous.com


Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>