check_partition() stops its probe once it hits an I/O error from the
partition checkers.  This would prevent the actual partition checker
getting a chance to verify the partition.

So this patch lets check_partition() continue probing untill it hits a
success while recording the I/O error which might have been reported by the
checking routines.

Also, it does some cleanup of the partition methods for ibm, atari and
amiga to return -1 upon hitting an I/O error.

Signed-off-by: Suzuki K P <suzuki@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>