mtd: nand: pxa3xx: return error code of nand_scan_ident() on error

The nand_scan_ident() returns an appropriate error value when it
fails.  Use it instead of the fixed error code -ENODEV.
(This driver is already doing so for nand_scan_tail().)

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>