st/nine: Fix the calculation of the number of vs inputs
st/nine: Fix the calculation of the number of vs inputs

Fixes hangs on radeonsi, and assert on llvmpipe.

Signed-off-by: Axel Davy <axel.davy@ens.fr>

Cc: "12.0" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler