spi: pxa2xx: Move platform driver to a separate file

The spi-pxa2xx.c is bloated with a platform driver code while
pretending to provide a core functionality. Make it real core
library by splitting out the platform driver to a separate file.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://msgid.link/r/20240530151117.1130792-11-andriy.shevchenko@linux.intel.com


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