The AMD SPI driver uses devm_ioremap_resource() to map its registers, so
they're automatically unmapped via device_release() when the last ref on
the SPI controller is dropped.  The additional iounmap() in the ->probe()
error path is thus unnecessary.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/497cc38ae2beb7900ae05a1463eb83ff96e2770e.1588590210.git.lukas@wunner.deSigned-off-by: Mark Brown <broonie@kernel.org>