broadcom/qpu: define v3d_qpu_input, use on v3d_qpu_alu_instr

broadcom/qpu: define v3d_qpu_input, use on v3d_qpu_alu_instr

At this point it just tidy up a little the alu_instr structure.

But also serves to prepare the structure for new changes, as 7.x uses
raddr instead of mux, and it is just easier to add the raddr to the
new input structure.

Signed-off-by: Alejandro Piñeiro <apinheiro@igalia.com>
Signed-off-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25450>