i965: Drop the remaining default predication whacking.

i965: Drop the remaining default predication whacking.

With my earlier cleaning in place (see git log brw_eu_emit.c), nothing
relies on the instruction emitters for IF/WHILE/JMPI disabling
predication.  Drop it in favor of making callers do the right thing
explicitly.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>