svga: move svga_update_state() call in draw code

svga: move svga_update_state() call in draw code

This fixes a few Piglit transform feedback regressions caused by
commit 7a1401938b351.

In that change I moved the moved svga_update_state() into the loops,
after the calls to svga_hwtnl_set_flatshade().  But
svga_hwtnl_set_flatshade() actually depends on some derived shader
state.  This patch moves the svga_update_state() call into
svga_draw_vbo() so it's not duplicated in two places.

Fixes: 7a1401938b351 ("svga: clean up retry_draw_range_elements(),
retry_draw_arrays()")

Reviewed-by: Charmaine Lee <charmainel@vmware.com>