Add error messages to the probe call.

[adaplas]
On failure, return actual error value instead of -ENXIO.
Signed-off-by: NMaciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: NAntonino Daplas <adaplas@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>