uboot-phytec

sf: Add extended read commands support

Current sf uses FAST_READ command, this patch adds support to
use the different/extended read command.

This implementation will determine the fastest command by taking
the supported commands from the flash and the controller, controller
is always been a priority.

Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>