flash: nxp: enabling lpc55s36's FMC

This commit enables the SoC's flash memory controller.

 - added lpc55s36 specific code in the NXP MCUX driver
   to take advantage of the SoC's check-before-read
   capability
 - enabled the FMC node in the SoC's dtsi (iap)
 - added the flash controller chosen node to the board's dts

Signed-off-by: Yves Vandervennet <yves.vandervennet@nxp.com>