i965: Update stale comment about unused VUE map slots.
i965: Update stale comment about unused VUE map slots.

I changed this from COUNT to PAD in commit 268008f98c3810b9f276df985dc93ef.

Signed-off-by: Kenneth Graunke <bd2562f754ec92342f93f61c25d731e290a2ffa8@whitecape.org>
Reviewed-by: Chris Forbes <5dcac483e7a6e31a5cbe89f38cc69dff8ee93dac@ijw.co.nz>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler