drm/rockchip: dsi: switch to FIELD_PREP_WM16* macros

The era of hand-rolled HIWORD_UPDATE macros is over, at least for those
drivers that use constant masks.

Remove this driver's HIWORD_UPDATE macro, and replace instances of it
with either FIELD_PREP_WM16 or FIELD_PREP_WM16_CONST, depending on
whether they're in an initializer. This gives us better error checking,
which already saved me some trouble during this refactor.

The driver's HIWORD_UPDATE macro doesn't shift up the value, but expects
a pre-shifted value. Meanwhile, FIELD_PREP_WM16 and
FIELD_PREP_WM16_CONST will shift the value for us, based on the given
mask. So a few things that used to be a HIWORD_UPDATE(VERY_LONG_FOO,
VERY_LONG_FOO) are now a somewhat more pleasant
FIELD_PREP_WM16(VERY_LONG_FOO, 1).

There are some non-trivial refactors here. A few literals needed a UL
suffix added to stop them from unintentionally overflowing as a signed
long. To make sure all of these cases are caught, and not just the ones
where the FIELD_PREP_WM16* macros use such a value as a mask, just mark
every literal that's used as a mask as unsigned.

Non-contiguous masks also have to be split into multiple
FIELD_PREP_WM16* instances, as the macro's checks and shifting logic
rely on contiguous masks.

This is compile-tested only.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>