spi: fix misleading controller deregistration kernel-doc
The controller reference count is not decremented on deregistration if
the controller has been allocated using devm_spi_alloc_host/target().
Amend the kernel-doc for devm_spi_register_controller() and
spi_unregister_controller() so that it reflects this (more recent)
behaviour.
Fixes: 5e844cc37a5c ("spi: Introduce device-managed SPI controller allocation")
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20260312151817.32100-6-johan@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>