MIPS: Remove pr_<level> uses of KERN_<level>

These would result in KERN_<level> actually getting printed.

Signed-off-by: Joe Perches <joe@perches.com>
To: Jiri Kosina <trivial@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/1581/


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