This patch added support to save environment to spi. User
need to enable CONFIG_ENV_IS_IN_SPI_FLASH. This patch also
added support to enable CONFIG_ENV_SIZE, CONFIG_ENV_OFFSET
and CONFIG_ENV_SECT_SIZE through Kconfig.
Signed-off-by: Vipul Kumar <vipul.kumar@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>