Convert CONFIG_FLASH_CFI_DRIVER et al to Kconfig

This converts the following to Kconfig:
   CONFIG_FLASH_CFI_DRIVER
   CONFIG_SYS_FLASH_USE_BUFFER_WRITE
   CONFIG_FLASH_CFI_MTD
   CONFIG_SYS_FLASH_PROTECTION
   CONFIG_SYS_FLASH_CFI

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Re-migrate]
Signed-off-by: Tom Rini <trini@konsulko.com>