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 <david.daney@cavium.com>
Signed-off-by: Andreas Herrmann <andreas.herrmann@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: kvm@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/7006/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/r4k_switch.S

@@ -28,6 +28,7 @@
  */
 #define ST_OFF (_THREAD_SIZE - 32 - PT_SIZE + PT_STATUS)
 
+#ifndef USE_ALTERNATE_RESUME_IMPL
 /*
  * task_struct *resume(task_struct *prev, task_struct *next,
  *		       struct thread_info *next_ti, s32 fp_save)
@@ -99,6 +100,8 @@
 	jr	ra
 	END(resume)
 
+#endif /* USE_ALTERNATE_RESUME_IMPL */
+
 /*
  * Save a thread's fp context.
  */