soc: nxp: rw: define Kconfigs for MEMC_MCUX_FLEXSPI code relocation

MEMC_MCUX_FLEXSPI depends on code relocation being enabled on parts that
XIP from the FlexSPI by default and requires a string describing the RAM
region to relocate code into. Add these Kconfigs to the RW SOC port.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>