MIPS: Rewrite clearing of ll_bit on context switch in C

This also means there is now only one implementation not 3 left.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/system.h

@@ -66,16 +66,11 @@ do {									\
 #define __mips_mt_fpaff_switch_to(prev) do { (void) (prev); } while (0)
 #endif
 
-#ifdef CONFIG_CPU_HAS_LLSC
-#define __clear_software_ll_bit() do { } while (0)
-#else
-extern unsigned long ll_bit;
-
 #define __clear_software_ll_bit()					\
 do {									\
-	ll_bit = 0;							\
+	if (!__builtin_constant_p(cpu_has_llsc) || !cpu_has_llsc)	\
+		ll_bit = 0;						\
 } while (0)
-#endif
 
 #define switch_to(prev, next, last)					\
 do {									\