RT75957. twr-k70f120m: NAND Flash support; environment in flash
This patch consists of the following: 1. NAND Flash Controller (NFC) pin configuration. 2. NFC clock configuration (enable the clock, initialize the clock rate.) 3. Changes to the `fsl_nfc` NFC driver: * Code cleanup (there were compilation warnings, e.g. unused data and functions.) * `#include <asm/immap.h>` should not be used on ARM. * Disable the GPIO configuration code on ARM. * Use `__raw_writel/__raw_readl` instead of `out_be32/in_be32`. The registers of the NAND Flash Controller always use the same endianness as the MCU core. * Make the code in fsl_nfc_get_id() and fsl_nfc_get_status() endianness-independent (they were accessing the data from 32-bit register as an array of u8, this approach is endianness-dependent.) 4. NAND support in the U-Boot configuration file. 5. Support for environment in the NAND flash in the U-Boot configuration file. 6. Increase the size of the `RAM` memory region to fit the statically allocated data for the NAND driver and the U-Boot framework for NAND.
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