i965: Fix brw_vs_prog_data_compare to actually check field members.

i965: Fix brw_vs_prog_data_compare to actually check field members.

&a and &b are the address of the local stack variables, not the actual
structures.  Instead of comparing the fields of a and b, we compared
...some stack memory.

Caught by Valgrind on Piglit's glsl-lod-bias test (among many others).

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=68233
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Cc: mesa-stable@lists.freedesktop.org