arm: socfpga: dts: Add Cadence QSPI DT node to socfpga.dtsi

arm: socfpga: dts: Add Cadence QSPI DT node to socfpga.dtsi

This DT node is taken from the Rocketboard.org Linux repsitory. And
is needed to enable (configure) the Cadence DM SPI driver.

Signed-off-by: Stefan Roese <[email protected]>
Cc: Chin Liang See <[email protected]>
Cc: Dinh Nguyen <[email protected]>
Cc: Vince Bridgers <[email protected]>
Cc: Marek Vasut <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Simon Glass <[email protected]>
Cc: Jagannadha Sutradharudu Teki <[email protected]>