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.