spi: Add compatible string for brcmstb SoCs

Add compatible string for brcmstb 7445 SoCs.
Signed-off-by: Ray Jui <ray.jui@broadcom.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20200910152539.45584-1-ray.jui@broadcom.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/spi/brcm,spi-bcm-qspi.txt

@@ -32,6 +32,8 @@ Required properties:
     			     			  			    BRCMSTB  SoCs
     "brcm,spi-bcm7435-qspi", "brcm,spi-bcm-qspi", "brcm,spi-brcmstb-mspi" : Second Instance of MSPI
     			     			  			    BRCMSTB  SoCs
+    "brcm,spi-bcm7445-qspi", "brcm,spi-bcm-qspi", "brcm,spi-brcmstb-mspi" : Second Instance of MSPI
+                                                                            BRCMSTB  SoCs
     "brcm,spi-bcm7216-qspi", "brcm,spi-bcm-qspi", "brcm,spi-brcmstb-mspi" : Second Instance of MSPI
     			     			  			    BRCMSTB  SoCs
     "brcm,spi-bcm7278-qspi", "brcm,spi-bcm-qspi", "brcm,spi-brcmstb-mspi" : Second Instance of MSPI