mmc: meson-gx: constify member data of struct meson_host

Constify member data of struct meson_host. This also allows to remove
the cast as of_device_get_match_data() returns a const void *.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/70e5520f-e327-111d-9ea4-824460e41561@gmail.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>