tests: drivers: spi: spi_loopback: added overlay file for mimxrt1170

Added an overlay file for mimxrt1170_evk_cm33 to test rtio
with the spi_loopback test.
Added mimxrt1170_evk_cm7 to the testcase.yml file

Signed-off-by: Emilio Benavente <emilio.benavente@nxp.com>