arm/pgtable: remove duplicate included header file

The header file asm-generic/pgtable-nopud.h is included whether CONFIG_MMU
is defined or not.

Include it only once before the #ifndef/#else/#endif preprocessor
directives and remove the following make includecheck warning:

  asm-generic/pgtable-nopud.h is included more than once

Link: https://lkml.kernel.org/r/20250219112403.3959-2-thorsten.blum@linux.dev


Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>