Add support for various boot devices like NAND, QSPINOR, SPINOR, eMMC, EIMNOR, SATA.
Modify board level files to support the feature and add corresponding defconfig files
Signed-off-by: Ye Li
CONFIG_ARM=y CONFIG_ARCH_MX7=y CONFIG_TARGET_MX7DSABRESD=y CONFIG_IMX_RDC=y CONFIG_IMX_BOOTAUX=y CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/freescale/mx7dsabresd/imximage.cfg,SYS_BOOT_QSPI" CONFIG_CMD_GPIO=y CONFIG_CMD_DHCP=y CONFIG_CMD_PING=y
