watchdog: ulp_wdog: guard reset_cpu with condition check

There will be build error if CONFIG_SYSRESET is enabled, so guard
the reset_cpu with condition check here

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/watchdog/ulp_wdog.c b/drivers/watchdog/ulp_wdog.c
index c21aa3a..0eea04e 100644
--- a/drivers/watchdog/ulp_wdog.c
+++ b/drivers/watchdog/ulp_wdog.c
@@ -122,6 +122,7 @@
 	ulp_watchdog_init(wdog, CONFIG_WATCHDOG_TIMEOUT_MSECS);
 }
 
+#if !CONFIG_IS_ENABLED(SYSRESET)
 void reset_cpu(void)
 {
 	struct wdog_regs *wdog = (struct wdog_regs *)WDOG_BASE_ADDR;
@@ -159,6 +160,7 @@
 
 	while (1);
 }
+#endif
 
 static int ulp_wdt_start(struct udevice *dev, u64 timeout_ms, ulong flags)
 {