MIPS: kernel: syscall: Set the appropriate ISA level for MIPS R6

MIPS R6 changed the opcodes for LL/SC instructions so we need to set
the appropriate ISA level.

Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>

arch/mips/kernel/syscall.c

@@ -136,7 +136,7 @@ static inline int mips_atomic_set(unsigned long addr, unsigned long new)
 		: "memory");
 	} else if (cpu_has_llsc) {
 		__asm__ __volatile__ (
-		"	.set	arch=r4000				\n"
+		"	.set	"MIPS_ISA_ARCH_LEVEL"			\n"
 		"	li	%[err], 0				\n"
 		"1:	ll	%[old], (%[addr])			\n"
 		"	move	%[tmp], %[new]				\n"