powerpc/64: don't select ARCH_HAS_SCALED_CPUTIME on book3E

Book3E doesn't have SPRN_SPURR/SPRN_PURR.

Activating ARCH_HAS_SCALED_CPUTIME is just wasting CPU time.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://github.com/linuxppc/issues/issues/171
Link: https://lore.kernel.org/r/a8b567c569aa521a7cf1beb061d43d79070e850c.1566492229.git.christophe.leroy@c-s.fr

arch/powerpc/Kconfig

@@ -133,7 +133,7 @@ config PPC
 	select ARCH_HAS_PTE_DEVMAP		if PPC_BOOK3S_64
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_MEMBARRIER_CALLBACKS
-	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE && PPC64
+	select ARCH_HAS_SCALED_CPUTIME		if VIRT_CPU_ACCOUNTING_NATIVE && PPC_BOOK3S_64
 	select ARCH_HAS_STRICT_KERNEL_RWX	if ((PPC_BOOK3S_64 || PPC32) && !RELOCATABLE && !HIBERNATION)
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UACCESS_FLUSHCACHE