posix main: avoid declaring px4_main_t, include the correct header instead

platforms/posix/src/main.cpp

@@ -53,6 +53,7 @@
 #include "DriverFramework.hpp"
 #include <termios.h>
 #include <sys/stat.h>
+#include <px4_tasks.h>
 
 namespace px4
 {
@@ -61,8 +62,6 @@ void init_once();
 
 using namespace std;
 
-typedef int (*px4_main_t)(int argc, char *argv[]);
-
 #define CMD_BUFF_SIZE	100
 
 #ifdef PATH_MAX