anv/blit2d: Add another passthrough varying to the VS
anv/blit2d: Add another passthrough varying to the VS

We need the VS to provide some setup data for other stages.

Reviewed-by: Nanley Chery <d78cd5d33e98a5581566f188959f731bd0b1c0fd@intel.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler