drivers: clock_control: Remove unused 'sys' argument

The 'sys' argument in clock_control_renesas_ra_get_rate() is unused and
has been removed to clean up the implementation.

This also aligns with the function's actual behavior and eliminates
misleading validation logic.

Signed-off-by: Gaetan Perrot <[email protected]>

Author: moonlight83340

drivers/clock_control/clock_control_renesas_ra_cgc.c

@@ -71,11 +71,13 @@ static int clock_control_renesas_ra_off(const struct device *dev, clock_control_
 static int clock_control_renesas_ra_get_rate(const struct device *dev, clock_control_subsys_t sys,
 					     uint32_t *rate)
 {
+	ARG_UNUSED(sys);
+
 	const struct clock_control_ra_pclk_cfg *config = dev->config;
 	uint32_t clk_src_rate;
 	uint32_t clk_div_val;
 
-	if (!dev || !sys || !rate) {
+	if (!dev || !rate) {
 		return -EINVAL;
 	}