i965: Bump Ivybridge's fake MRF range to g112-127 instead of g111-126.

i965: Bump Ivybridge's fake MRF range to g112-127 instead of g111-126.

When I originally implemented the hack to use GRFs 111+ as fake MRFs, I
did so purely to avoid rewriting all the code that dealt with MRFs.
However, it turns out that a similar hack is actually required.

Newly discovered language in the BSpec indicates that SEND instructions
with EOT set "should" use g112-g127 as their source registers.  Based on
assertions in the simulator, this is actually a requirement on certain
platforms.

Since we're faking MRFs already, we may as well use the officially
sanctioned range.  My guess is that we avoided this issue because we
seldom use m0: URB writes in the new VS backend start at m1, and RT
writes in the new FS backend start at m2.

NOTE: This is a candidate for stable release branches.

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