mtd: m25p80: Fix false-positive probing

mtd: m25p80: Fix false-positive probing

Since commit 18c6182bae0acca220ed6611f741034d563cd19f ("Rework
probing/JEDEC code"), m25p80 driver successfully registers chips
even if JEDEC probing fails.

This was needed to support non-JEDEC flashes. Though, it appears
that some platforms (e.g. blackfin bf533 stamp[1]) used the old
behavior to detect if there's any flash connected, so the driver
have to fail on JEDEC probing errors.

This patch restores the old behavior for JEDEC flashes, and adds
"-nonjedec" SPI device IDs for M25Pxx flashes, so that the kernel
still supports non-JEDEC flashes.

[1] http://blackfin.uclinux.org/gf/project/uclinux-dist/tracker/?action=TrackerItemEdit&tracker_item_id=5975

Reported-by: Mingquan Pan
Reported-by: Barry Song <21cnbao@gmail.com>
Signed-off-by: Anton Vorontsov <avorontsov@mvista.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>