sf: winbond: Add support for W25Q256

Add support for Winbond W25Q256 SPI flash.

Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
1 file changed