radv: SDMA v4 size field is size - 1

After cross-checking with kernel and the old buffer copy code, it seems
that the size field should be size - 1 instead.

Fixes: 7b5ab48c40b ("radv: partial sdma support")

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21585>
(cherry picked from commit e9a55b332a3fb5acfc551f10f30f7d0961e85f27)
2 files changed