powerpc/85xx: Don't use generic timebase sync on 64-bit

85xx currently uses the generic timebase sync mechanism when
CONFIG_KEXEC is enabled, because 32-bit 85xx kexec support does a hard
reset of each core.  64-bit 85xx kexec does not do this, so we neither
need nor want this (nor is the generic timebase sync code built on
ppc64).

FWIW, I don't like the fact that the hard reset is done on 32-bit
kexec, and I especially don't like the timebase sync being triggered
only on the presence of CONFIG_KEXEC rather than actually booting in
that environment, but that's beyond the scope of this patch...
Signed-off-by: Scott Wood <scottwood@freescale.com>

arch/powerpc/platforms/85xx/smp.c

@@ -344,7 +344,7 @@ struct smp_ops_t smp_85xx_ops = {
 	.cpu_disable	= generic_cpu_disable,
 	.cpu_die	= generic_cpu_die,
 #endif
-#ifdef CONFIG_KEXEC
+#if defined(CONFIG_KEXEC) && !defined(CONFIG_PPC64)
 	.give_timebase	= smp_generic_give_timebase,
 	.take_timebase	= smp_generic_take_timebase,
 #endif