MIPS: asm: fpu: Allow 64-bit FPU on MIPS32 R6

MIPS32 R6 has a 64-bit FPU so add the necessary MIPS R6
definition.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

arch/mips/include/asm/fpu.h

@@ -68,7 +68,8 @@ static inline int __enable_fpu(enum fpu_mode mode)
 		goto fr_common;
 
 	case FPU_64BIT:
-#if !(defined(CONFIG_CPU_MIPS32_R2) || defined(CONFIG_64BIT))
+#if !(defined(CONFIG_CPU_MIPS32_R2) || defined(CONFIG_CPU_MIPS32_R6) \
+      || defined(CONFIG_64BIT))
 		/* we only have a 32-bit FPU */
 		return SIGFPE;
 #endif