spi: atmel-quadspi: add support for SAM9X7 QSPI controller

Add support for the QuadSPI controller found on the SAM9X7 SoC.

This controller does not implement pad calibration. It supports
operation up to 100 MHz, and requires the GCK to run at twice
the data rate.

Signed-off-by: Varshini Rajendran <varshini.rajendran@microchip.com>
Signed-off-by: Dharma Balasubiramani <dharma.b@microchip.com>
Link: https://patch.msgid.link/20250908-microchip-qspi-v2-4-8f3d69fdd5c9@microchip.com


Signed-off-by: Mark Brown <broonie@kernel.org>