drm/rockchip: vop2: switch to FIELD_PREP_WM16 macro

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

Remove VOP2's HIWORD_UPDATE macro from the vop2 header file, and replace
all instances in rockchip_vop2_reg.c (the only user of this particular
HIWORD_UPDATE definition) with equivalent FIELD_PREP_WM16 instances. This
gives us better error checking.

Reviewed-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Tested-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
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>