drivers: clock_control: imx: Simplify pointer casting.

Use `uintptr_t` to cast a pointer to integer type for `clock_name`.
While at it, also remove an unused variable.

Signed-off-by: Artur Rojek <[email protected]>

Author: ar-conclusive

drivers/clock_control/clock_control_mcux_ccm.c

@@ -60,12 +60,7 @@ static int mcux_ccm_get_subsys_rate(const struct device *dev,
 				    clock_control_subsys_t sub_system,
 				    uint32_t *rate)
 {
-#ifdef CONFIG_ARM64
-	uint32_t clock_name = (uint32_t)(uint64_t) sub_system;
-#else
-	uint32_t clock_name = (uint32_t) sub_system;
-#endif
-	uint32_t mux __unused;
+	uint32_t clock_name = (uintptr_t)sub_system;
 
 	switch (clock_name) {