ocfs2: delete unnecessary checks before three function calls

kfree(), ocfs2_free_path() and __ocfs2_free_slot_info() test whether their
argument is NULL and then return immediately.  Thus the test around their
calls is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
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>