dt-bindings: spi: atmel-quadspi: QuadSPI driver for Microchip SAM9X60

The sam9x60 qspi controller uses 2 clocks, one for the peripheral register
access, the other for the qspi core and phy. Both are mandatory.
Signed-off-by: NTudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: NBoris Brezillon <bbrezillon@kernel.org>
Signed-off-by: NMark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/atmel-quadspi.txt

 * Atmel Quad Serial Peripheral Interface (QSPI)
 
 Required properties:
-- compatible:     Should be "atmel,sama5d2-qspi".
+- compatible:     Should be one of the following:
+		  - "atmel,sama5d2-qspi"
+		  - "microchip,sam9x60-qspi"
 - reg:            Should contain the locations and lengths of the base registers
                   and the mapped memory.
 - reg-names:      Should contain the resource reg names:
                   - qspi_base: configuration register address space
                   - qspi_mmap: memory mapped address space
 - interrupts:     Should contain the interrupt for the device.
-- clocks:         The phandle of the clock needed by the QSPI controller.
-- clock-names:    Should contain "pclk" for the peripheral clock.
+- clocks:         Should reference the peripheral clock and the QSPI system
+                  clock if available.
+- clock-names:    Should contain "pclk" for the peripheral clock and "qspick"
+                  for the system clock when available.
 - #address-cells: Should be <1>.
 - #size-cells:    Should be <0>.