drivers: haptics: Fix drv2605 C++ compatibility

Add `extern "C"` guard around the function declarations in drv2605.h.
Without this guard, compiling code with a C++ compiler fails due to name
mangling issues.

Signed-off-by: Manu Sutela <manu.sutela@gmail.com>

Author: MJAS1

include/zephyr/drivers/haptics/drv2605.h

@@ -9,6 +9,10 @@
 #include <zephyr/drivers/haptics.h>
 #include <zephyr/types.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define DRV2605_WAVEFORM_SEQUENCER_MAX 8
 
 enum drv2605_library {
@@ -83,4 +87,8 @@ union drv2605_config_data {
 int drv2605_haptic_config(const struct device *dev, enum drv2605_haptics_source source,
 			  const union drv2605_config_data *config_data);
 
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
 #endif