mtd: m25p80: Reinstate error print on unrecognized flash

mtd: m25p80: Reinstate error print on unrecognized flash

Commit 35f5589ba7c1c2389eccc0821cbfeefe3cc7d445 removed the
"unrecognized JEDEC id" error message, causing the probe function to
silently abort if the flash ID is unrecognized.

It is desirable to produce diagnostic output in this situation so that
the user has some idea what went wrong.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>