DOC: kernel-parameters.txt: Mark `nofpu' for MIPS too

The MIPS port has supported this option since forever, long before SH
was even in plans.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9665/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>