tests: drivers: pwm: Change pwm channel for ek_ra6m3

Change default pwm to pwm0 on ek_ra6m3 in test app pwm_loopback
to avoid pin conflict with ethernet phy.

Signed-off-by: Ta Minh Nhat <nhat-minh.ta.yn@bp.renesas.com>

Author: Ta Minh Nhat

tests/drivers/pwm/pwm_loopback/boards/ek_ra6m3.overlay

@@ -11,7 +11,7 @@
 	pwm_loopback_0 {
 		compatible = "test-pwm-loopback";
 		/* first index must be a 32-Bit timer */
-		pwms = <&pwm1 0 0 PWM_POLARITY_NORMAL>,
+		pwms = <&pwm0 0 0 PWM_POLARITY_NORMAL>,
 			<&pwm4 0 0 PWM_POLARITY_NORMAL>;
 	};
 };