powerpc: Shield code specific to 64-bit server processors

This is a random collection of added ifdef's around portions of
code that only mak sense on server processors. Using either
CONFIG_PPC_STD_MMU_64 or CONFIG_PPC_BOOK3S as seems appropriate.

This is meant to make the future merging of Book3E 64-bit support
easier.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 7d46e5d..8564a41 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -117,6 +117,7 @@
 	if (!en)
 		return;
 
+#ifdef CONFIG_PPC_STD_MMU_64
 	if (firmware_has_feature(FW_FEATURE_ISERIES)) {
 		/*
 		 * Do we need to disable preemption here?  Not really: in the
@@ -134,6 +135,7 @@
 		if (local_paca->lppaca_ptr->int_dword.any_int)
 			iseries_handle_interrupts();
 	}
+#endif /* CONFIG_PPC_STD_MMU_64 */
 
 	/*
 	 * if (get_paca()->hard_enabled) return;