ocfs2: do not log twice error messages

'o2hb_map_slot_data' and 'o2hb_populate_slot_data' are called from only
one place, in 'o2hb_region_dev_write'.  Return value is checked and
'mlog_errno' is called to log a message if it is not 0.

So there is no need to call 'mlog_errno' directly within these functions.
This would result on logging the message twice.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>