MIPS: DEC: Do not set up the FPU interrupt if no FPU

MIPS: DEC: Do not set up the FPU interrupt if no FPU

Following the arrangement for processors that wire FPU exceptions to the
FPE CPU exception handle the case where no FPU is in use -- which for
DECstation systems will only ever happen when the "nofpu" kernel option
has been used -- do not register the FPU interrupt in such a case
either.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9714/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>