jit: avoid using __vector in testcase [PR110466]

jit: avoid using __vector in testcase [PR110466]

r13-4531-gd2e782cb99c311 added test coverage to libgccjit's vector
support, but used __vector, which doesn't work on Power.  Additionally
the size param to gcc_jit_type_get_vector was wrong.

Fixed thusly.

gcc/testsuite/ChangeLog:
	PR jit/110466
	* jit.dg/test-expressions.c (run_test_of_comparison): Fix size
	param to gcc_jit_type_get_vector.
	(verify_comparisons): Use a typedef rather than __vector.

Co-authored-by: Marek Polacek <polacek@redhat.com>
Signed-off-by: David Malcolm <dmalcolm@redhat.com>