intel/fs: Fix fs_inst::flags_read for ANY/ALL predicates

Without this, we were DCEing flag writes because we didn't think their
results were used because we didn't understand that an ANY32 predicate
actually read all the flags.

Fixes: df1aec76 "i965/fs: Define methods to calculate the flag..."
Reviewed-by: Matt Turner <mattst88@gmail.com>
(cherry picked from commit 6c858b9a)