spi: pxa2xx: Add SSC2 and SSPSP2 SSP registers

Update list of SSP registers with SSC2 and SSPSP2. These registers are
utilized by LPT/WPT AudioDSP architecture.

While SSC2 shares the same offset (0x40) as SSACDD, description of this
register for SSP device present on mentioned AudioDSP is different so
define separate constant to avoid any ambiguity.

Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Cezary Rojewski <cezary.rojewski@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200825201743.4926-1-cezary.rojewski@intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>