Silicon/NXP: Add function to return swapped Mmio APIs pointer

Add support to return pointer to MMIO APIs on basis of Swap flag.
If Flag is True then MMIO APIs returned in which data
swapped after reading from MMIO and before write using MMIO.

Signed-off-by: Meenakshi Aggarwal <meenakshi.aggarwal@nxp.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>