panfrost: Remove postfix parameter from UBO upload

panfrost: Remove postfix parameter from UBO upload

Need to signal push constants via a side channel. I tried to disentangle
this code, but there are a number of stacked issues here:

* We need to upload sysvals. Currently we prefix UBO #0 with sysvals,
  but this requires a memcpy() of the entire contents of UBO #0. We
  could create a synthetic UBO instead with sysvals at the end.

* We want to push uniforms/sysvals. Currently we push UBO #0 as much as
  we can, which pushes sysvals automatically by point 1.

* We want to optimize out f2f16(uniform). We don't currently handle
  this.

* We want to optimize out uniform-on-uniform/constant operations. Mesa
  doesn't currently have good support for this.

The real solution will look something like:

* Create a separate UBO for sysvals.

* Let the compiler allocate push constant space as it sees fit ("copy
  word 12:15 of UBO 1 to word 2:3 of push constant space, as fp16").

* Somehow handle uniform folding when NIR gains support.

For now, let's not block the depostfixening.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6476>