spi: pxa2xx: Get rid of unused ->cs_control()

Since the last user of the custom ->cs_control() gone, we may get rid of
this legacy API completely.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20211123192723.44537-2-andriy.shevchenko@linux.intel.com


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