drivers: memc: introduce driver for APS6408L PSRAM

Introduce driver for APS6408L PSRAM, built on top of the MCUX memc
driver for flexSPI. This driver supports operating the PSRAM in high
speed mode (200MHz or more). Note that in order to support this
PSRAM's alignment requirements, either ahb-read-addr-opt or
ahb-prefetch must be set for the FlexSPI instance.

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