arm: socfpga: vining: Set default SPI NOR mode and frequency

The SPI NOR bus mode is 0 on this system, update it accordingly.
Increase frequency to 40 MHz and enable SFDP parsing, since the
flashes on this system support that and it is a huge performance
improvement.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Siew Chin Lim <elly.siew.chin.lim@intel.com>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Cc: Tien Fong Chee <tien.fong.chee@intel.com>