spi: fsl-espi: improve and extend register bit definitions

Add definition of further register bits for use in upcoming
driver extensions and improve current bit definitions:
- use BIT macro
- use bit names as in the chip spec

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
1 file changed