i965/fs: Try a different pre-scheduling heuristic if the first spills.

i965/fs: Try a different pre-scheduling heuristic if the first spills.

Since LIFO fails on some shaders in one particular way, and non-LIFO
systematically fails in another way on different kinds of shaders, try
them both, and pick whichever one successfully register allocates first.
Slightly prefer non-LIFO in case we produce extra dependencies in register
allocation, since it should start out with fewer stalls than LIFO.

This is madness, but I haven't come up with another way to get unigine
tropics to not spill while keeping other programs from not spilling and
retaining the non-unigine performance wins from texture-grf.

total instructions in shared programs: 1626728 -> 1626288 (-0.03%)
instructions in affected programs:     1015 -> 575 (-43.35%)
GAINED:                                50
LOST:                                  0

Improves Unigine Tropics performance by 14.5257% +/- 0.241838% (n=38)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70445
Cc: "10.0" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>