MIPS: Remove CONFIG_PMCTWILED completely

Commit 8b284dbc2200 ("MIPS: PNX Removing dead CONFIG_PMCTWILED") missed
one reference to CONFIG_PMCTWILED in the code. It also missed one
related reference to pmctwiled_setup(). Remove these references now.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/6957/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>