board: arm: Add board support for mimxrt1024_evk

Add board support files for mimxrt1024_evk, the development board for
i.MXRT1024(CM7) SoC.

- Add pinmux, dts, doc.
- Code can be loaded to SRAM.
- Tested samples: hello_world, philosophers, synchronization,
basic/blinky, and basic/button.

Signed-off-by: Lucien Zhao <lucien.zhao@nxp.com>