MIPS: Remove pointless return statement from empty void functions.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
To: Sergei Shtylyov <sshtylyov@mvista.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2391/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>