i965: Fix GPU hangs on Broadwell in shaders with some control flow.

i965: Fix GPU hangs on Broadwell in shaders with some control flow.

According to the documentation, we need to set the source 0 register
type to IMM for flow control instructions that have both JIP and UIP.

Fixes GPU hangs in approximately 10 Piglit tests, 5 es3conform tests,
Unigine Crypt, a WebGL raytracer demo, and several Steam titles.

Cc: "10.2" <mesa-stable@lists.freedesktop.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75478
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75878
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76939
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Tested-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Tested-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>