xfs: remove XLOG_STATE_IOABORT

This value is the only flag in ic_state, which we otherwise use as
a state.  Switch it to a new debug-only field and also report and
actual error in the buffer in the I/O completion path.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>