mips: DEC: honor CONFIG_MIPS_FP_SUPPORT=n

Include the DECstation interrupt handler in opting out of
FPU support.

Fixes a linker error:

mips-linux-ld: arch/mips/dec/int-handler.o: in function `fpu':
(.text+0x148): undefined reference to `handle_fpe_int'

Fixes: 183b40f992c8 ("MIPS: Allow FP support to be disabled")
Signed-off-by: Randy Dunlap <[e-mail]>
Reported-by: kernel test robot <[e-mail]>
Cc: Paul Burton <[e-mail]>
Cc: Thomas Bogendoerfer <[e-mail]>
Cc: Maciej W. Rozycki <[e-mail]>
Cc: [e-mail]
Acked-by: Maciej W. Rozycki <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/dec/int-handler.S

···
 		 */
 		mfc0	t0,CP0_CAUSE		# get pending interrupts
 		mfc0	t1,CP0_STATUS
-#ifdef CONFIG_32BIT
+#if defined(CONFIG_32BIT) && defined(CONFIG_MIPS_FP_SUPPORT)
 		lw	t2,cpu_fpu_mask
 #endif
 		andi	t0,ST0_IM		# CAUSE.CE may be non-zero!
···
 
 		beqz	t0,spurious
 
-#ifdef CONFIG_32BIT
+#if defined(CONFIG_32BIT) && defined(CONFIG_MIPS_FP_SUPPORT)
 		 and	t2,t0
 		bnez	t2,fpu			# handle FPU immediately
 #endif
···
 		j	dec_irq_dispatch
 		 nop
 
-#ifdef CONFIG_32BIT
+#if defined(CONFIG_32BIT) && defined(CONFIG_MIPS_FP_SUPPORT)
 fpu:
 		lw	t0,fpu_kstat_irq
 		nop

arch/mips/dec/setup.c

···
 		dec_interrupt[DEC_IRQ_HALT] = -1;
 
 	/* Register board interrupts: FPU and cascade. */
-	if (dec_interrupt[DEC_IRQ_FPU] >= 0 && cpu_has_fpu) {
+	if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT) &&
+	    dec_interrupt[DEC_IRQ_FPU] >= 0 && cpu_has_fpu) {
 		struct irq_desc *desc_fpu;
 		int irq_fpu;