drivers: pinctrl: nrf: add flag to signal the FAST_ACTIVE1 peripherals

This patch introduces a new flag to indicate if a peripheral belongs
to FAST_ACTIVE1 domain. This way, pinctrl knows when to request the
SLOW_ACTIVE domain (where CTRLSEL multiplexer resides).

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>