spi: zynq-qspi: Enhance the Linear CFG bit definitions

Using masks makes sense when manipulating fields of several bits. When
only one bit is involved, it is usual to just use the BIT() macro but
in this case using the term mask is abusive. Fix the #define macros
and their comments.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20191108140744.1734-5-miquel.raynal@bootlin.com


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