soc: nordic_nrf: move NFCT_PINS_AS_GPIOS to common nRF definitions

Kconfig symbol NFCT_PINS_AS_GPIOS may be defined for all
Nordic nRF SoCs that have the NFCT hardware, so we move
the option definition in nRF common Kconfig file. Also,
we correct the help text to reflect that nRF52 series DKs
and nRF5340 DK have different pins for NFC.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>