spi: amd: Drop redundant check

Both spi and spi-mem cores already take care of checking the minimum and
maximum speed for transfers depending on the controller
capabilities. There is no reason to repeat this check in controller
drivers.

Once this possible error condition removed from the function, it makes
no longer sense to return an int.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://patch.msgid.link/20241224-winbond-6-11-rc1-quad-support-v2-4-ad218dbc406f@bootlin.com


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