Fix missing variable, types, includes and comments

hw-tests/api-demo/api/api_caller.c

 void* api_call_start (uint32_t id, void* args, size_t size)
 {
+	int ret;
 	// aquire semaphore
 	ret = SEMA_GetSema (API_CALL_SEMA);
 

hw-tests/api-demo/api/api_caller.h

 #include "api_common.h"
 
-int api_call (uint32_t id, void *args);
+void* api_call (uint32_t id, void *args, size_t size);
+void* api_call_bother_dispatcher (void* buf);

hw-tests/api-demo/api/api_common.h

+#include <stdint.h>
+
 #define API_CALL_SEMA 0
 
 struct api_call
 {
 	uint32_t id;
 	uint8_t returning;
-	unsigned char *buf;
+	unsigned char buf[1];
 };
 
 static struct api_call **ApiCallSpace = (void*)0x20080001;

hw-tests/api-demo/api/api_dispatcher.c

@@ -6,6 +6,10 @@ api_init (sys_cfg_sema_t *sys_cfg)
 	int ret;
 
 	ret = SEMA_Init (sys_cfg);
+	/* Set the status of the flag to a valid initial state (right before
+	 * api-calls are made) */
 	ApiCallSpace->returning = 1;
+
+	return ret;
 }
 

hw-tests/api-demo/api/api_dispatcher.h

 #include "api_common.h"
+#include "mxc_sys.h"
 
 int
 api_init (sys_cfg_sema_t *sys_cfg);