pinctrl: meson: axg: Fix PIN and BANK offsets

Periphs bank offset must be applied on all pins and
PMX bank to prevent issue in meson_pinconf_set call.
Without offset on pins when a call to pinconf is done
meson_gpio_calc_reg_and_bit return wrong offset.
To avoid breaking pmx function offset is needed in pmx bank structure too.

Signed-off-by: Guillaume La Roque <glaroque@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>