drivers: spi: Fix spi_loopback failure for Renesas RZ/G3S-SMARC

Fixes the `spi_loopback` test failure on board Renesas `rzg3s_smarc` since
the test has been updated by /pull/86383

Signed-off-by: Quang Le <[email protected]>
Signed-off-by: Tien Nguyen <[email protected]>

Author: le-quang168