Input: cypress-sf - add Cypress StreetFighter touchkey driver

Input: cypress-sf - add Cypress StreetFighter touchkey driver

This adds support for Cypress StreetFighter touchkey controllers such
as sf3155. This driver supports managing regulators and generating
input events.

Due to lack of documentation, this driver is entirely based on
information gathered from a driver written for an old Android kernel
fork[1][2].

[1] https://github.com/LineageOS/android_kernel_xiaomi_msm8996/blob/lineage-18.1/drivers/input/touchscreen/cyttsp_button.c
[2] https://github.com/LineageOS/android_kernel_xiaomi_msm8996/blob/lineage-18.1/arch/arm/boot/dts/qcom/a4-msm8996-mtp.dtsi#L291-L314

Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
Link: https://lore.kernel.org/r/20210907174341.422013-2-y.oudjana@protonmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>