arm: socfpga: Add example config entry for EPCS/EPCQ SPI

arm: socfpga: Add example config entry for EPCS/EPCQ SPI

Add example config file entry for the Altera SPI controller. This SPI
controller can also, under special conditions, be used to operate the
EPCS/EPCQ SPI NOR.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Vince Bridgers <vbridger@altera.com>
Cc: Pavel Machek <pavel@denx.de>
Cc: Stefan Roese <sr@denx.de>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>