uboot-imx

sf: Add spi_flash_read_bar

Add spi_flash_read_bar function for reading bar and
discovering bar commands at probe time.

Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Jagan Teki <jteki@openedev.com>