spi: Remove code duplication in spi_add_device*()

The commit 0c79378c ("spi: add ancillary device support")
added a dozen of duplicating lines of code. We may move them
to the __spi_add_device(). Note, that the code may be called
under the mutex.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20230714091748.89681-2-andriy.shevchenko@linux.intel.com


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