ARM: mcpm: use -st dsb option prior to sev instructions

In a similar manner to our spinlock implementation, mcpm uses sev to
wake up cores waiting on a lock when the lock is unlocked. In order to
ensure that the final write unlocking the lock is visible, a dsb
instruction is executed immediately prior to the sev.

This patch changes these dsbs to use the -st option, since we only
require that the store unlocking the lock is made visible.
Acked-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Dave Martin <dave.martin@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm/common/mcpm_head.S

@@ -151,7 +151,7 @@ mcpm_setup_leave:
 
 	mov	r0, #INBOUND_NOT_COMING_UP
 	strb	r0, [r8, #MCPM_SYNC_CLUSTER_INBOUND]
-	dsb
+	dsb	st
 	sev
 
 	mov	r0, r11

arch/arm/common/vlock.S

@@ -42,7 +42,7 @@
 	dmb
 	mov	\rscratch, #0
 	strb	\rscratch, [\rbase, \rcpu]
-	dsb
+	dsb	st
 	sev
 .endm
 
@@ -102,7 +102,7 @@ ENTRY(vlock_unlock)
 	dmb
 	mov	r1, #VLOCK_OWNER_NONE
 	strb	r1, [r0, #VLOCK_OWNER_OFFSET]
-	dsb
+	dsb	st
 	sev
 	bx	lr
 ENDPROC(vlock_unlock)