freedreno/a3xx: WFI fixes/cleanup

Blob driver seems to need WFI in some cases after CP_EVENT_WRITE,
implying that this is asynchronous and should reset needs_wfi.
Also, CP_INVALIDATE_STATE seems to need WFI.  But CP_LOAD_STATE
does not.

The blob driver also puts WFIs before writing GRAS_CL_VPORT registers.
The latter may be a work-around, as these registers should be banked/
context registers.  I haven't yet found a lockup that this averts, but
I expect viewport to change infrequently so out of paranoia I will
keep these for now.

Signed-off-by: Rob Clark <robclark@freedesktop.org>
freedreno: use util_copy_framebuffer_state()

Signed-off-by: Rob Clark <robclark@freedesktop.org>