Fixed overzealous px4_ prefixing

Some files had px4_px4_ prefixed functions.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/systemcmds/reboot/reboot.c

@@ -65,7 +65,7 @@ int reboot_main(int argc, char *argv[])
 		}
 	}
 
-	systemreset(to_bootloader);
+	px4_systemreset(to_bootloader);
 }