mtd: cfi_cmdset_0002: Use right chip in do_ppb_xxlock()

do_ppb_xxlock() fails to add chip->start when querying for lock status
(and chip_ready test), which caused false status reports.
Fix that by adding adr += chip->start and adjust call sites
accordingly.

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>