powerpc/powermac: mark smp_psurge_{give,take}_timebase static

These functions are only called locally and should be static like the
other corresponding functions are:

arch/powerpc/platforms/powermac/smp.c:416:13: error: no previous prototype for 'smp_psurge_take_timebase' [-Werror=missing-prototypes]
  416 | void __init smp_psurge_take_timebase(void)
      |             ^~~~~~~~~~~~~~~~~~~~~~~~
arch/powerpc/platforms/powermac/smp.c:432:13: error: no previous prototype for 'smp_psurge_give_timebase' [-Werror=missing-prototypes]
  432 | void __init smp_psurge_give_timebase(void)
      |             ^~~~~~~~~~~~~~~~~~~~~~~~
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231108125843.3806765-20-arnd@kernel.org

arch/powerpc/platforms/powermac/smp.c

@@ -413,7 +413,7 @@ static void __init smp_psurge_setup_cpu(int cpu_nr)
 		printk(KERN_ERR "Couldn't get primary IPI interrupt");
 }
 
-void __init smp_psurge_take_timebase(void)
+static void __init smp_psurge_take_timebase(void)
 {
 	if (psurge_type != PSURGE_DUAL)
 		return;
@@ -429,7 +429,7 @@ void __init smp_psurge_take_timebase(void)
 	set_dec(tb_ticks_per_jiffy/2);
 }
 
-void __init smp_psurge_give_timebase(void)
+static void __init smp_psurge_give_timebase(void)
 {
 	/* Nothing to do here */
 }