The number of dynamic descriptors is limited by both the number of
descriptors and the total number of dynamic things. Because there isn't
a single "maximum dynamic things" limit, we need to divide by two so
that they can create the maximum of both UBOs and SSBOs.
Reviewed-by: Eduardo Lima Mitev <elima@igalia.com> Cc: "17.0 13.0" <mesa-stable@lists.freedesktop.org>