i965: Clean up code for VS pull constant surface creation.

i965: Clean up code for VS pull constant surface creation.

Like for the WM pull constants, we can merge the former prepare/emit
stages into one tracked state atom.  Furthermore, the code that used to
handle the binding table was removed in the last commit, leaving some
rather silly looking short functions that can easily be folded in.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>