st/glsl_to_tgsi: mark "gaps" in input/output arrays as used

st/glsl_to_tgsi: mark "gaps" in input/output arrays as used

In some cases, a shader may have an input/output array but not use some
entries in the middle. This happens with eON games, for example.

We emit declarations that cover the entire array range even if there are
some unused gaps. This patch now reflects that in the InputsRead etc.
fields to ensure the various input/outputMapping arrays are actually
correct, which will be important when we re-jiggle the way declarations
are emitted.

v2: fix a typo (Edward O'Callaghan)

Reviewed-by: Edward O'Callaghan <funfunctor@folklore1984.net>
Reviewed-by: Dave Airlie <airlied@redhat.com>