ocfs2: less function calls in ocfs2_convert_inline_data_to_extents() after error detection

kfree() was called in a few cases by ocfs2_convert_inline_data_to_extents()
during error handling even if the passed variable "pages" contained a
null pointer.

* Return from this implementation directly after failure detection for
  the function call "kcalloc".

* Corresponding details could be improved by the introduction of another
  jump label.

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>