qoriq: add support for NXP T4240RDB board

qoriq: add support for NXP T4240RDB board

Hardware specs:
  - NXP T4240, 12C/24T @ 1.67 GHz
  - 3 × 2 GB DDR3 SO-DIMM
  - 128 MB NOR flash
  - 2 GB SLC NAND
  - SD card interface
  - PCIe: x4 and x8
  - SATA 3 Gbps
  - 8 × 1 GbE
  - 4 × 10 GbE SFP
  - RTC

This commit adds two sysupgrade image types:
  - nor:    boot and run the entire system from NOR
  - sdboot: boot and run the entire system from SD card

How to obtain and install factory images:
  - At the moment U-Boot support is not mergeable because it requires
    the mpc85xx toolchain to build.
  - Please follow the instructions in the GitHub PR:
    https://github.com/openwrt/openwrt/pull/10941

Signed-off-by: Pawel Dembicki <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/10941
Signed-off-by: Stijn Tintel <[email protected]>