drivers: clock_control: litex: add missing include

Drivers uses custom IO read/write API defined in soc.h.

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>

drivers/clock_control/clock_control_litex.c

@@ -18,6 +18,8 @@
 #include <stdio.h>
 #include <zephyr/kernel.h>
 
+#include <soc.h>
+
 LOG_MODULE_REGISTER(CLK_CTRL_LITEX, CONFIG_CLOCK_CONTROL_LOG_LEVEL);
 
 static struct litex_clk_device *ldev;	/* global struct for whole driver */