mtd: rawnand: Fix and simplify again the continuous read derivations

We need to avoid the first page if we don't read it entirely.
We need to avoid the last page if we don't read it entirely.
While rather simple, this logic has been failed in the previous
fix. This time I wrote about 30 unit tests locally to check each
possible condition, hopefully I covered them all.

Reported-by: Christophe Kerello <christophe.kerello@foss.st.com>
Closes: https://lore.kernel.org/linux-mtd/20240221175327.42f7076d@xps-13/T/#m399bacb10db8f58f6b1f0149a1df867ec086bb0a


Suggested-by: Christophe Kerello <christophe.kerello@foss.st.com>
Fixes: 828f6df1

 ("mtd: rawnand: Clarify conditions to enable continuous reads")
Cc: stable@vger.kernel.org
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Christophe Kerello <christophe.kerello@foss.st.com>
Link: https://lore.kernel.org/linux-mtd/20240223115545.354541-2-miquel.raynal@bootlin.com