mips/cavium-octeon: Fix typo *must* in comment

Fixes: 5b3b1688 ("MIPS: Add Cavium OCTEON processor support files to arch/mips/cavium-octeon.")
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@vger.kernel.org