drm/msm/registers: Generate _HI/LO builders for reg64

drm/msm/registers: Generate _HI/LO builders for reg64

The upstream mesa copy of the GPU regs has shifted more things to reg64
instead of seperate 32b HI/LO reg32's.  This works better with the "new-
style" c++ builders that mesa has been migrating to for a6xx+ (to better
handle register shuffling between gens), but it leaves the C builders
with missing _HI/LO builders.

So handle the special case of reg64, automatically generating the
missing _HI/LO builders.

Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/673559/