MIPS: Cleanup forgotten label_module_alloc in tlbex.c

commit c8af165342e83a4eb078c9607d29a7c399d30a53 (lmo) rsp.
e0cc87f5

 (kernel.org) left
label_module_alloc unused.  Remove it now.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/752/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>