ARMv7: Check whether the SMP/nAMP mode was already enabled

If running in non-secure mode, enabling this register will fault.
Signed-off-by: Tony Thompson <Anthony.Thompson@arm.com>
Acked-by: Srinidhi Kasagar <srinidhikasagar@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm/mm/proc-v7.S

@@ -186,9 +186,10 @@ cpu_v7_name:
  */
 __v7_setup:
 #ifdef CONFIG_SMP
-	mrc	p15, 0, r0, c1, c0, 1		@ Enable SMP/nAMP mode and
-	orr	r0, r0, #(1 << 6) | (1 << 0)	@ TLB ops broadcasting
-	mcr	p15, 0, r0, c1, c0, 1
+	mrc	p15, 0, r0, c1, c0, 1
+	tst	r0, #(1 << 6)			@ SMP/nAMP mode enabled?
+	orreq	r0, r0, #(1 << 6) | (1 << 0)	@ Enable SMP/nAMP mode and
+	mcreq	p15, 0, r0, c1, c0, 1		@ TLB ops broadcasting
 #endif
 	adr	r12, __v7_setup_stack		@ the local stack
 	stmia	r12, {r0-r5, r7, r9, r11, lr}