boards: nxp: mcxn947: enable the default MCU-Boot swap mode

- Enables MCU-Boot default Swap mode for the FRDM-MCXN947 and MCX-N9XX-EVK,
  after the flash driver was upgraded to support the 16-byte programming.
- Fixes flash-controller for frdm_mcxn947_mcxn947_cpu0_qspi.

Signed-off-by: Andrej Butok <andrey.butok@nxp.com>