i965/cnl: Add l3 configuration for Cannonlake

i965/cnl: Add l3 configuration for Cannonlake

V2 (Anuj):
Squash the changes in one patch rebase on master.
Address the review comments made by Francisco Jerez.
Do the URB allocation per slice (not per bank).

V3 (Anuj):
Update the comment.
Format the table as other l3 config tables.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
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V1 was sent out with the heading:
"i965/cnl: Properly handle l3 configuration"