spi: amd: Drop io_base_addr member from struct amd_spi

The io_base_addr member of struct amd_spi is not referenced anywhere
in the driver implementation and there is no indication that it could
be used in the future, hence drop it.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://lore.kernel.org/r/20220706100626.1234731-5-cristian.ciocaltea@collabora.com


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