ocfs2: remove kfree() redundant null checks

smatch analysis indicates a number of redundant NULL checks before
calling kfree(), eg:

  fs/ocfs2/alloc.c:6138 ocfs2_begin_truncate_log_recovery() info:
   redundant null check on *tl_copy calling kfree()

  fs/ocfs2/alloc.c:6755 ocfs2_zero_range_for_truncate() info:
   redundant null check on pages calling kfree()

etc....

[akpm@linux-foundation.org: revert dubious change in ocfs2_begin_truncate_log_recovery()]
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Acked-by: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>