ARM: 7921/1: mcpm: remove redundant dsb instructions prior to sev

sync_cache_w already includes a dsb, so we can just use sev() directly
then following a cache-sync.

Acked-by: Dave Martin <[e-mail]>
Acked-by: Nicolas Pitre <[e-mail]>
Signed-off-by: Will Deacon <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

arch/arm/common/mcpm_entry.c

···
 	dmb();
 	mcpm_sync.clusters[cluster].cpus[cpu].cpu = CPU_DOWN;
 	sync_cache_w(&mcpm_sync.clusters[cluster].cpus[cpu].cpu);
-	dsb_sev();
+	sev();
 }
 
 /*
···
 	dmb();
 	mcpm_sync.clusters[cluster].cluster = state;
 	sync_cache_w(&mcpm_sync.clusters[cluster].cluster);
-	dsb_sev();
+	sev();
 }
 
 /*