Merge changes from topic "imx8mp-tbbr" into integration

* changes:
  feat(plat/imx/imx8m/imx8mp): enable Trusted Boot
  feat(plat/imx/imx8m/imx8mp): add in BL2 with FIP
  refactor(plat/imx/imx8m): make image load logic for TBBR FIP booting common
  feat(plat/imx/imx8m/imx8mp): add initial definition to facilitate FIP layout
  refactor(plat/imx/imx): make imx io-storage logic for TBBR/FIP common
  feat(plat/imx/imx8m/imx8mp): add imx8mp_private.h to the build