spi: dw: Fix typo in few registers name

This patch will fix typo in the register name used in the source code,
to be consistent with the register name used in the databook.

Databook: DW_apb_ssi_databook.pdf version 4.01a

Signed-off-by: Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200505130618.554-2-wan.ahmad.zainie.wan.mohamad@intel.com


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