spi: pxa2xx: Update header block in pxa2xx_ssp.h

We have direct users of some headers that are missed and
have header included when forward declarations are enough.

Update header block in pxa2xx_ssp.h to align with actual usage.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200826151455.55970-1-andriy.shevchenko@linux.intel.com


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