sf: Add bank addr code in CONFIG_SPI_FLASH_BAR

Defined bank addr code on CONFIG_SPI_FLASH_BAR macro, to reduce the
size for existing boards which has < 16Mbytes SPI flashes.

It's upto user which has provision to use the bank addr code for
flashes which has > 16Mbytes.

Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>