powerpc/mm/highmem: Switch to generic kmap atomic

No reason having the same code in every architecture

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20201103095858.087635810@linutronix.de

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e9f13fe..d4cfddc 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -409,6 +409,7 @@
 config HIGHMEM
 	bool "High memory support"
 	depends on PPC32
+	select KMAP_LOCAL
 
 source "kernel/Kconfig.hz"