mtd: pxa3xx_nand: Fix blank page ECC mismatch

mtd: pxa3xx_nand: Fix blank page ECC mismatch

commit 543e32d5ff165d0d68deedb0e3557478c7c36a4a upstream.

This bug was introduced in f8155a40 ("mtd: pxa3xx_nand: rework irq
logic") and causes the PXA3xx NAND controller fail to operate with NAND
flash that has empty pages. According to the comment in this block, the
hardware controller will report a double-bit error for empty pages,
which can and must be ignored.

This patch restores the original behaviour of the driver.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Acked-by: Lei Wen <leiwen@marvell.com>
Cc: Haojian Zhuang <haojian.zhuang@marvell.com>
Cc: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>