intel/compiler: fix loading of draw_id from task & mesh payload

intel/compiler: fix loading of draw_id from task & mesh payload

Previously both destination and source were floats, so no casting was
performed, but with 7664c85b1da source register was reinterpreted as
unsigned integer, so MOV started casting that integer to float.

Fixes: 7664c85b1da ("intel/compiler: Create and use struct for TASK and MESH thread payloads")
Reviewed-by: Caio Oliveira <caio.oliveira@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18886>