spi: Kill spi_add_device_locked()

Now, spi_add_device_locked() has just a line on top of __spi_add_device().
Besides that, it has a single caller. So, just kill it and embed its parts
into the caller.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230714091748.89681-3-andriy.shevchenko@linux.intel.com


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