spi: bcm-qspi: Add compatible string for BRCMSTB 7445 SoCs

Add compatible string for BRCMSTB 7445 SoCs and indicate it has MSPI rev
support.

Signed-off-by: Ray Jui <ray.jui@broadcom.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20200910152539.45584-2-ray.jui@broadcom.com


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