aco: improve creation of v_madmk_f32/v_madak_f32

aco: improve creation of v_madmk_f32/v_madak_f32

Using needs_vop3 check was flawed because it would only combine the
literal if the first operand is the literal. If the second or third
operand is the literal, then needs_vop3 will be true and the literal will
not be combined.

pipeline-db (Navi):
Totals from affected shaders:
SGPRS: 782051 -> 782051 (0.00 %)
VGPRS: 630048 -> 630048 (0.00 %)
Spilled SGPRs: 195 -> 195 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Code Size: 54743740 -> 54585548 (-0.29 %) bytes
Max Waves: 67340 -> 67340 (0.00 %)
Instructions: 10182030 -> 10182030 (0.00 %)

pipeline-db (Vega):
Totals from affected shaders:
SGPRS: 701990 -> 699590 (-0.34 %)
VGPRS: 566632 -> 566784 (0.03 %)
Spilled SGPRs: 218 -> 218 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Code Size: 49173564 -> 49007856 (-0.34 %) bytes
Max Waves: 59650 -> 59612 (-0.06 %)
Instructions: 9315135 -> 9293330 (-0.23 %)

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2883>