timing: Fix symbol extern for C++

This commit adds `extern "C"` to `timing.h` so that C function names do
not get mangled when including this header file from a C++ source file.

Signed-off-by: Stephanos Ioannidis <[email protected]>

Author: stephanosio

include/zephyr/timing/timing.h

@@ -10,6 +10,10 @@
 #include <zephyr/sys/arch_interface.h>
 #include <zephyr/timing/types.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void soc_timing_init(void);
 void soc_timing_start(void);
 void soc_timing_stop(void);
@@ -175,4 +179,8 @@ static inline uint32_t timing_freq_get_mhz(void)
  * @}
  */
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif /* ZEPHYR_INCLUDE_TIMING_TIMING_H_ */