spi: Remove check for idling in __spi_pump_messages()

Since the whole idling transition is locked by the io_mutex now, there is
no need to check this flag anymore.

Signed-off-by: David Jander <david@protonic.nl>
Link: https://lore.kernel.org/r/20220621061234.3626638-7-david@protonic.nl


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