powerpc/mem: Fix arch/powerpc/mm/mem.c:53:12: error: no previous prototype for 'create_section_mapping'

Commit 8e11d62e2e87 ("powerpc/mem: Add back missing header to fix 'no
previous prototype' error") was supposed to fix the problem, but in
the meantime commit a927bd6ba952 ("mm: fix phys_to_target_node() and*
memory_add_physaddr_to_nid() exports") moved create_section_mapping()
prototype from asm/sparsemem.h to asm/mmzone.h

Fixes: 8e11d62e2e87 ("powerpc/mem: Add back missing header to fix 'no previous prototype' error")
Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Christophe Leroy <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/025754fd[e-mail]

arch/powerpc/mm/mem.c

···
 #include <asm/machdep.h>
 #include <asm/rtas.h>
 #include <asm/kasan.h>
-#include <asm/sparsemem.h>
 #include <asm/svm.h>
+#include <asm/mmzone.h>
 
 #include <mm/mmu_decl.h>