Fixed warnings issued by new xt-clang compiler

New Xtensa xt-clang driver issues new warnings that were not
present before when using xt-xcc driver.

Fixed warnings related to enum cast to other enum by removing
"frame_fmt" local variable assignment in the selector.c file.
Assignment was not needed in the build_config function body, as the
variable "frame_fmt" is passed in the next line to
audio_stream_fmt_conversion function, that writes to this variable as
output.

Silenced warnings related to C/C++ interoperability.

Signed-off-by: Andrey Borisovich <andrey.borisovich@intel.com>

Author: Andrey Borisovich

src/audio/selector/selector.c

@@ -579,14 +579,12 @@ static void build_config(struct comp_data *cd, struct module_config *cfg)
 	enum sof_ipc_frame __sparse_cache frame_fmt, valid_fmt;
 	int i;
 
-	frame_fmt = cfg->base_cfg.audio_fmt.depth;
 	audio_stream_fmt_conversion(cfg->base_cfg.audio_fmt.depth,
 				    cfg->base_cfg.audio_fmt.valid_bit_depth,
 				    &frame_fmt, &valid_fmt,
 				    cfg->base_cfg.audio_fmt.s_type);
 	cd->source_format = frame_fmt;
 
-	frame_fmt = cd->sink_format;
 	audio_stream_fmt_conversion(cd->output_format.depth,
 				    cd->output_format.valid_bit_depth,
 				    &frame_fmt, &valid_fmt,

src/include/sof/audio/module_adapter/iadk/system_service.h

@@ -13,6 +13,11 @@
 
 #include <stdint.h>
 
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wextern-c-compat"
+#endif //__clang__
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -233,4 +238,8 @@ struct SystemService : public AdspSystemService {};
 }
 #endif
 
+#ifdef __clang__
+#pragma clang diagnostic pop // ignored "-Wextern-c-compat"
+#endif //__clang__
+
 #endif /* _ADSP_SYSTEM_SERVICE_H_ */