panfrost: Move sampler/tex descs emission helpers to pan_cmdstream.c

panfrost: Move sampler/tex descs emission helpers to pan_cmdstream.c

Move panfrost_upload_texture_descriptors() and
panfrost_upload_sampler_descriptors() to pan_cmdstream.c where other
cmdstream related helpers live. While at it, change their prototype
and name to make it consistent with the other helpers and prepare
things for ctx->payloads[] removal.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4083>