i965: Disable ARB_fragment_shader_interlock for platforms prior to GEN9

ARB_fragment_shader_interlock depends on memory fences to
ensure fragment ordering and this ordering guarantee is
only supported from GEN9 onwards.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109980


Fixes: 93931270 "i965: Add ARB_fragment_shader_interlock support."
Signed-off-by: Plamena Manolova <plamena.n.manolova@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
(cherry picked from commit 19ab0820)