drivers: pinctrl_nrf: : Allow applying pins of disabled peripherals

According to the nrfx peripheral resource sharing example in
samples/boards/nrf/nrfx_prs it should be possible to share a resource
and apply the pins on peripheral that share resource ID.
However the sample only works since it only demonstrates UART and SPIM,
and by enabling both another SPIM driver, and UART is enabled for the
console. It would not be possible to enable a TWIM driver in addition.
Instead allow the PSELs if the configuration for NRFX has been enabled.

Signed-off-by: Joakim Andersson <joerchan@gmail.com>