spi: bcm-qspi: Fix probe regression on iProc platforms

iProc chips have QSPI controller that does not have the MSPI_REV
offset. Reading from that offset will cause a bus error. Fix it by
having MSPI_REV query disabled in the generic compatible string.

Fixes: 3a01f04d

 ("spi: bcm-qspi: Handle lack of MSPI_REV offset")
Link: https://lore.kernel.org/linux-arm-kernel/20200909211857.4144718-1-f.fainelli@gmail.com/T/#u
Signed-off-by: Ray Jui <ray.jui@broadcom.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20200910152539.45584-3-ray.jui@broadcom.com
Signed-off-by: Mark Brown <broonie@kernel.org>