Because PPB unlocking unlocks the whole chip cfi_ppb_unlock() needs to
remember the locked status for each sector so it can re-lock the
unaddressed sectors. Dynamically calculate the maximum number of sectors
rather than using a hardcoded value that is too small for larger chips.
Tested with Spansion S29GL01GS11TFI flash device.
Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>