i965/fs/generator: Don't use the address immediate for MOV_INDIRECT

i965/fs/generator: Don't use the address immediate for MOV_INDIRECT

The address immediate field is only 9 bits and, since the value is in
bytes, the highest GRF we can point to with it is g15.  This makes it
pretty close to useless for MOV_INDIRECT.  There were already piles of
restrictions preventing us from using it prior to Broadwell, so let's get
rid of the gen8+ code path entirely.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97779
Cc: "12.0 13.0" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>