spi: spi-qpic-snand: simplify bad block marker duplication

Due to the expectations of the SPINAND code, the driver duplicates
the bad block markers during raw OOB reads.

It has been implemented by using two if statements, and due to the
opposite conditions one of conditional codepaths always runs. Since
the effect of both codepaths is the same, remove the if statements
and use a single line solution instead.

Also add a note about why the duplication is required.

No functional changes intended.

Signed-off-by: Gabor Juhos <j4g8y7@gmail.com>
Link: https://patch.msgid.link/20250711-qpic-snand-simplify-bbm-copy-v1-1-dd2608325f72@gmail.com


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