anv: Don't add dynamic state base address to push constants on Gen7

anv: Don't add dynamic state base address to push constants on Gen7

Because Gen7 push constants are already relative to dynamic state base
address, they aren't really an address.  It's deceptive to return an
address from the helper function.  Instead, let's leave it as a
special-case in the gen7-11 helper; we don't need the helper for code
de-duplication for Gen7 anyway.

Fixes: 67d2cb3e9367a "anv: Add get_push_range_address() helper"
Closes: #2323
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>