img: Simplify the open_image() macro

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

image.c

@@ -210,6 +210,9 @@ struct cr_img *open_image_at(int dfd, int type, unsigned long flags, ...)
 	va_list args;
 	int ret;
 
+	if (dfd == -1)
+		dfd = get_service_fd(IMG_FD_OFF);
+
 	img = xmalloc(sizeof(*img));
 	if (!img)
 		goto errn;

include/image.h

@@ -138,7 +138,7 @@ extern int open_image_dir(char *dir);
 extern void close_image_dir(void);
 
 extern struct cr_img *open_image_at(int dfd, int type, unsigned long flags, ...);
-#define open_image(typ, flags, ...) open_image_at(get_service_fd(IMG_FD_OFF), typ, flags, ##__VA_ARGS__)
+#define open_image(typ, flags, ...) open_image_at(-1, typ, flags, ##__VA_ARGS__)
 extern struct cr_img *open_pages_image(unsigned long flags, struct cr_img *pmi);
 extern struct cr_img *open_pages_image_at(int dfd, unsigned long flags, struct cr_img *pmi);
 extern void up_page_ids_base(void);