The formula for calculating these two values seems to depend on
tess_use_shared, ie. a6xx_gen3 and a6xx_gen4 match.  The existing
calculation matches a6xx_gen1 and a6xx_gen2.

The new formula is based on traces varying # of output (from VS)
varyings from (1..31)*vec4 and vertices from (1..31) and coming up
with something that matches the blob.  Once hs_input_size*4 divided
by tcs_vertices_out goes above 64, this deviates a bit from the
blob, but AFAICT it is safe to pick a larger values.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <mesa/mesa!12497>