spi: rockchip: Support 64-location deep FIFOs

The FIFO depth of SPI V2 is 64 instead of 32, add support for it.

Signed-off-by: Jon Lin <jon.lin@rock-chips.com>
Tested-by: Emil Renner Berthing <kernel@esmil.dk>
Reviewed-by: Emil Renner Berthing <kernel@esmil.dk>
Link: https://lore.kernel.org/r/20200723004356.6390-2-jon.lin@rock-chips.com


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