mtd: nand: pxa3xx_nand: write exactly one message on probe failure

For some error paths alloc_nand_resource() emitted an error message, for
others it didn't. Make it consistently print a message including the
error code where it's not constant and drop the hardly helpful
additional message printed by the caller of alloc_nand_resource.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>