MIPS: Remove a temporary hack for debugging cache flushes in SMTC configuration

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: aaro.koskinen@iki.fi
Cc: david.daney@cavium.com
Cc: linux-kernel@vger.kernel.org
Cc: markos.chandras@imgtec.com
Cc: dengcheng.zhu@imgtec.com
Cc: chenhc@lemote.com
Cc: akpm@linux-foundation.org
Patchwork: https://patchwork.linux-mips.org/patch/8535/