i965: Advertise larger line widths.

i965: Advertise larger line widths.

We've artificially been limiting this to 5 for no particular reason.

On Gen4-5, the limit is [0, 7.5] with a granularity of 0.5 (U3.1).
On Gen6+, the limit is [0, 7.9921875].  Since it's a U3.7, the
granularity should be 0.125 (1/8).

This patch conservatively advertises one granularity smaller than the
hardware's maximum value, just in case there's a problem using the
largest possible value.  On Gen4-5, this is 7.5 - 0.5 = 7.0.  On Gen6+,
this is 8.0 - 0.125 = 7.875.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>