ITE: dts: it82xx2: Add missing extend setting of alternate function

If I2C3 switches from GPH1/GPH2 to GPB2/GPB5, extend setting
is required.

Test: Accessing I2C is normal if I2C2, I2C3, I2C5 are switched.

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