i965: Fix failure to upload new constant data when changing programs.

i965: Fix failure to upload new constant data when changing programs.

This is fallout from the ffvertex_prog.c work.  It doesn't call
ProgramStringNotify, so we don't set param_state, so we wouldn't track when
VP parameters changed, and constants wouldn't get uploaded.  Instead, remove
param_state entirely and just use the real value that we want to be tracking.

Fixes rendering in openarena since BRW_NEW_BATCH got disentangled from
BRW_NEW_INDICES.

Bug #18822.