i965: Make brw_JMPI set predicate_control based on a parameter.

i965: Make brw_JMPI set predicate_control based on a parameter.

We use both predicated and unconditional JMPI instructions.  But in each
case, it's clear which we want.  It's simpler to just specify it as a
parameter, rather than relying on default state.

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