i965: Use arrays in Gen7+ URB code.

i965: Use arrays in Gen7+ URB code.

So much of this code was cut and pasted per stage.  We can accomplish
much of it by looping over shader stages.

Improves performance of OglBatch7 (version 6) by 1.50783% +/- 0.287049%
(n = 71) at 1024x768 on Cherryview.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>