freedreno/ir3: allow for additional VS sysval inputs

freedreno/ir3: allow for additional VS sysval inputs

There are a total of four possible currently, rather than 2.  So we need
to be prepared for the input array to grow by 16 components.  We could
get away with less if we could pack sysval inputs..  and the way this is
handled currently isn't really the nicest thing.  But it's a tactical
fix for an issue hit in:

GL31-CTS.gtf30.GL3Tests.transform_feedback.transform_feedback_vertex_id

Signed-off-by: Rob Clark <robclark@freedesktop.org>