tests: drivers: build_all: Add IT8801 mfd drivers test

Add build tests for the IT8801 MFD drivers, including GPIO,
Input and PWM functionalities.

GPIO, Input test: west build -p always -b native_sim
PWM test: west build -p always -b it82xx2_evb

Signed-off-by: Tim Lin <tim2.lin@ite.corp-partner.google.com>