ARM: dts: sam9x60: fix compatible for qspi child node

Change the compatible of the qspi child node to
`jedec,spi-nor` so that it can be properly found
when probing the bus.

Signed-off-by: Sergiu Moga <sergiu.moga@microchip.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>