powerpc/mm: Call mmu_context_init() from ppc64

Our 64-bit hash context handling has no init function, but 64-bit Book3E
will use the common mmu_context_nohash.c code which does, so define an
empty inline mmu_context_init() for 64-bit server and call it from
our 64-bit setup_arch()

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/kernel/setup_64.c

@@ -534,6 +534,10 @@ void __init setup_arch(char **cmdline_p)
 #endif
 
 	paging_init();
+
+	/* Initialize the MMU context management stuff */
+	mmu_context_init();
+
 	ppc64_boot_msg(0x15, "Setup Done");
 }