mtd: cfi_cmdset_0002: Fix unlocking requests crossing a chip boudary

The "sector is in requested range" test used to determine whether
sectors should be re-locked or not is done on a variable that is reset
everytime we cross a chip boundary, which can lead to some blocks being
re-locked while the caller expect them to be unlocked.
Fix the check to make sure this cannot happen.

Fixes: 1648eaaa ("mtd: cfi_cmdset_0002: Support Persistent Protection Bits (PPB) locking")
Cc: stable@vger.kernel.org
Signed-off-by: Joakim Tjernlund <joakim.tjernlund@infinera.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>