powerpc: Add jump label support

This patch adds support for the new "jump label" feature.

Unlike x86 and sparc we just merrily patch the code with no locks etc,
as far as I know this is safe, but I'm not really sure what the x86/sparc
code is protecting against so maybe it's not.

I also don't see any reason for us to implement the poke_early() routine,
even though sparc does.

[BenH: Updated the patch to upstream generic changes]

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2729c66..c15f2e6 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -134,6 +134,7 @@
 	select GENERIC_IRQ_SHOW_LEVEL
 	select HAVE_RCU_TABLE_FREE if SMP
 	select HAVE_SYSCALL_TRACEPOINTS
+	select HAVE_ARCH_JUMP_LABEL
 
 config EARLY_PRINTK
 	bool