pan/va: Add support for 64-bit atomic operations

Adds support for 64-bit atomic operations for KHR_shader_atomic_int64
using 64-bit atomic instructions. Valhall is working but Bifrost will
require some more work to implement as it requires two instructions to
execute a 64-bit atomic.

Reviewed-by: Mary Guillemard <mary.guillemard@collabora.com>
Reviewed-by: Eric R. Smith <eric.smith@collabora.com>
Signed-off-by: Ashley Smith <ashley.smith@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35789>
6 files changed