ARM: dts: at91: sama7g5ek: Add QSPI0 node

QSPI0 comunicates with a MX66LM1G45G SPI NOR flash.
Enable the controller and describe the flash.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20211209123643.341892-2-tudor.ambarus@microchip.com