Add format_write() that calls the write() function of the output

format. Have the raw format use image_copyout() for now.

format.c

@@ -65,3 +65,13 @@ format_selected(void)
 
 	return (format);
 }
+
+int
+format_write(int fd)
+{
+
+	if (format == NULL)
+		return (ENOSYS);
+
+	return (format->write(fd));
+}

format.h

@@ -42,5 +42,6 @@ SET_DECLARE(formats, struct mkimg_format);
 
 int	format_select(const char *);
 struct mkimg_format *format_selected(void);
+int	format_write(int);
 
 #endif /* _MKIMG_FORMAT_H_ */

mkimg.c

@@ -451,7 +451,7 @@ main(int argc, char *argv[])
 		fprintf(stderr, "Number of cylinders: %u\n", ncyls);
 	}
 
-	error = image_copyout(outfd);
+	error = format_write(outfd);
 	if (error)
 		errc(EX_IOERR, error, "writing image");
 

raw.c

@@ -40,10 +40,10 @@ __FBSDID("$FreeBSD$");
 #include "mkimg.h"
 
 static int
-raw_write(int fd __unused)
+raw_write(int fd)
 {
 
-	return (ENOSYS);
+	return (image_copyout(fd));
 }
 
 static struct mkimg_format raw_format = {