pan/mdg: Defer smul, vlut until after writeout moves

pan/mdg: Defer smul, vlut until after writeout moves

We can end up with bad dependencies with a depth/stencil export. Let's
let the writeout special cases consume these values if possible, using a
move otherwise in which case it won't be used in the other slots anyway.

total instructions in shared programs: 50508 -> 50507 (<.01%)
instructions in affected programs: 12 -> 11 (-8.33%)
helped: 1
HURT: 0

total bundles in shared programs: 25640 -> 25640 (0.00%)
bundles in affected programs: 0 -> 0
helped: 0
HURT: 0

total quadwords in shared programs: 40899 -> 40899 (0.00%)
quadwords in affected programs: 0 -> 0
helped: 0
HURT: 0

total registers in shared programs: 3917 -> 3916 (-0.03%)
registers in affected programs: 3 -> 2 (-33.33%)
helped: 1
HURT: 0

total threads in shared programs: 2455 -> 2455 (0.00%)
threads in affected programs: 0 -> 0
helped: 0
HURT: 0

total spills in shared programs: 168 -> 168 (0.00%)
spills in affected programs: 0 -> 0
helped: 0
HURT: 0

total fills in shared programs: 186 -> 186 (0.00%)
fills in affected programs: 0 -> 0
helped: 0
HURT: 0

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5513>