i965: Stop setting predication from brw_set_conditionalmod.

i965: Stop setting predication from brw_set_conditionalmod.

brw_set_conditionalmod has traditionally been complex: it causes
conditionalmod to be set for the next instruction, and then predication
to be set on all future instructions after that.

We may want to generate a flag condition and not use it immediately,
due to instruction scheduling or the like.  Even if not, it's easy
to set things explicitly, and that's clearer.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>