arm64: Use acquire/release semantics instead of explicit DMB

This patch changes the test_and_*_bit functions to use the
load-acquire/store-release instructions instead of explicit DMB.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/lib/bitops.S

@@ -46,13 +46,11 @@ ENTRY(	\name	)
 	mov	x2, #1
 	add	x1, x1, x0, lsr #3	// Get word offset
 	lsl	x4, x2, x3		// Create mask
-	smp_dmb	ish
-1:	ldxr	x2, [x1]
+1:	ldaxr	x2, [x1]
 	lsr	x0, x2, x3		// Save old value of bit
 	\instr	x2, x2, x4		// toggle bit
-	stxr	w5, x2, [x1]
+	stlxr	w5, x2, [x1]
 	cbnz	w5, 1b
-	smp_dmb	ish
 	and	x0, x0, #1
 3:	ret
 ENDPROC(\name	)