i965/fs: Don't use brw->fragment_program in calculate_urb_setup().

i965/fs: Don't use brw->fragment_program in calculate_urb_setup().

Reading brw->fragment_program is nonsensical in compiler code: it
contains the currently active program (if any), not the one currently
being compiled.  Attempting to access it may either lead to crashes
(null pointer dereference if no program is active) or wrong results.

Fixes piglit regressions since 9ef710575b914ddfc8e9a162d98ad554c1c217f7
on pre-Sandybridge hardware.  The actual bug was created in commit
7b1fbc688999fd568e65211d79d7678562061594.

NOTE: This is a candidate for the 8.0 branch.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=54183
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Paul Berry <stereotype441@gmail.com>
(cherry picked from commit 4d9abd96cc177cade79b64544096eb45bf8313a2)