pan/midgard: Fix scheduling mishap

pan/midgard: Fix scheduling mishap

We shouldn't try to schedule onto a vmul if the last unit was a smul;
that would force a break ("traveling back in time").

total bundles in shared programs: 2519 -> 2472 (-1.87%)
bundles in affected programs: 791 -> 744 (-5.94%)
helped: 20
HURT: 0
helped stats (abs) min: 1 max: 9 x̄: 2.35 x̃: 1
helped stats (rel) min: 1.52% max: 11.76% x̄: 7.94% x̃: 7.69%
95% mean confidence interval for bundles value: -3.47 -1.23
95% mean confidence interval for bundles %-change: -9.36% -6.51%
Bundles are helped.

total quadwords in shared programs: 4028 -> 3965 (-1.56%)
quadwords in affected programs: 1223 -> 1160 (-5.15%)
helped: 17
HURT: 0
helped stats (abs) min: 1 max: 17 x̄: 3.71 x̃: 2
helped stats (rel) min: 2.97% max: 10.64% x̄: 6.97% x̃: 7.14%
95% mean confidence interval for quadwords value: -5.71 -1.70
95% mean confidence interval for quadwords %-change: -8.03% -5.91%
Quadwords are helped.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>