MIPS: OCTEON: Enable use of FPU

MIPS: OCTEON: Enable use of FPU

Some versions of the assembler will not assemble CFC1 for OCTEON, so
override the ISA for these.

Add r4k_fpu.o to handle low level FPU initialization.

Modify octeon_switch.S to save the FPU registers.  And include
r4k_switch.S to pick up more FPU support.

Get rid of "#define cpu_has_fpu		0"

Signed-off-by: David Daney <[email protected]>
Signed-off-by: Andreas Herrmann <[email protected]>
Cc: [email protected]
Cc: James Hogan <[email protected]>
Cc: [email protected]
Patchwork: https://patchwork.linux-mips.org/patch/7006/
Signed-off-by: Ralf Baechle <[email protected]>