UPSTREAM: arm64/mm: add explicit struct_mm argument to __create_mapping()

Currently, swapper_pg_dir and idmap_pg_dir share the init_mm mm_struct
instance. To allow the introduction of other pg_dir instances, for instance,
for UEFI's mapping of Runtime Services, make the struct_mm instance an
explicit argument that gets passed down to the pmd and pte instantiation
functions. Note that the consumers (pmd_populate/pgd_populate) of the
mm_struct argument don't actually inspect it, but let's fix it for
correctness' sake.

Acked-by: Steve Capper <steve.capper@linaro.org>
Tested-by: Leif Lindholm <leif.lindholm@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

(cherry picked from commit e1e1fddae74b72d0415965821ad00fe39aac6f13)
Signed-off-by: Tomasz Figa <tfiga@chromium.org>

Bug: 24475017

Change-Id: Ia8733d9c5ec8eba58685bf5e13b6a680a9272b20
Signed-off-by: Kees Cook <keescook@google.com>