ARM: dts: alt: Add QSPI device to DT

Enable the QSPI controller in the alt device tree.

Based similar work for the silk board by by Vladimir Barinov and
Sergei Shtylyov.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>