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>

arch/powerpc/include/asm/book3s/64/mmu.h

@@ -107,6 +107,7 @@ extern int mmu_vmemmap_psize;
 extern int mmu_io_psize;
 
 /* MMU initialization */
+void mmu_early_init_devtree(void);
 extern void radix_init_native(void);
 extern void hash__early_init_mmu(void);
 extern void radix__early_init_mmu(void);