powerpc/mm: Add mmu_early_init_devtree()

Empty for now, but we'll add to it in the next patch.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
index 5447122..14220c5 100644
--- a/arch/powerpc/include/asm/mmu.h
+++ b/arch/powerpc/include/asm/mmu.h
@@ -210,6 +210,7 @@
 extern void early_init_mmu_secondary(void);
 extern void setup_initial_memory_limit(phys_addr_t first_memblock_base,
 				       phys_addr_t first_memblock_size);
+static inline void mmu_early_init_devtree(void) { }
 #endif /* __ASSEMBLY__ */
 #endif