Convert CONFIG_EMMC_BOOT et al to Kconfig

This converts the following to Kconfig:
   CONFIG_EMMC_BOOT
   CONFIG_MAC_ADDR_IN_SPIFLASH
   CONFIG_NAND_BOOT
   CONFIG_SPL_FSL_PBL
   CONFIG_SYS_FSL_DDR4

In this case we re-sync options that had been set in
CONFIG_SYS_EXTRA_OPTIONS but should not have been as they have proper
entries.

Signed-off-by: Tom Rini <trini@konsulko.com>