spi: spi-qpic-snand: extend FIELD_PREP() macro usage

spi: spi-qpic-snand: extend FIELD_PREP() macro usage

Large part of the code uses the FIELD_PREP() macro already to construct
values to be written to hardware registers. Change the code to use also
the macro for more registers of which the corresponding bitmasks are
defined already.

This makes the code more readable. It also syncs the affected
codes with their counterparts in the 'qcom_nandc' driver, so it
makes it easier to spot the differences between the two
implementations.

No functional changes intended.

Signed-off-by: Gabor Juhos <j4g8y7@gmail.com>
Reviewed-by: Md Sadre Alam <quic_mdalam@quicinc.com>
Link: https://patch.msgid.link/20250515-qpic-snand-use-bitmasks-v1-2-11729aeae73b@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>