sf: Fix quad bit set for micron devices

Setting up quad bit for micron devices need to do the
same way as other flash devices like spansion, winbond
etc does using enhanced volatile config register so this
patch adds this support instead of printing "QEB is volatile"

Cc: Simon Glass <sjg@chromium.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Cc: Peter Pan <peterpandong@micron.com>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Jagan Teki <jteki@openedev.com>