powerpc/smp: Declare current_set static

current_set extern not needed anymore since
commit eafd825e ("powerpc/64: Simplify __secondary_start
paca->kstack handling")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/a55eb65c9d7319f0af3c31e3f6ba36522f10003d.1646413435.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/asm-prototypes.h

@@ -20,7 +20,6 @@
 #include <uapi/asm/ucontext.h>
 
 /* SMP */
-extern struct task_struct *current_set[NR_CPUS];
 extern struct task_struct *secondary_current;
 void start_secondary(void *unused);
 

arch/powerpc/kernel/smp.c

@@ -716,7 +716,7 @@ void smp_send_stop(void)
 }
 #endif /* CONFIG_NMI_IPI */
 
-struct task_struct *current_set[NR_CPUS];
+static struct task_struct *current_set[NR_CPUS];
 
 static void smp_store_cpu_info(int id)
 {