i965/vs: Don't lower uniform array indexing.

i965/vs: Don't lower uniform array indexing.

This avoids the massive conditional move array access, and brings code
generation quality for the new VS backend into the realm of efficiency
of the old backend (roughly 20% more instructions generated than
before across shader-db, instead of assertion failing for generating
over 10,000 instructions on many shaders!).

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>