libv4l: add optional sdl2_image dependency

The configure.ac script simply uses PKG_CHECK_MODULES(), so there is
not --enable/--disable option.

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit b1ef2944a356c648ee04309de1b21bdfe5f46b4e)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libv4l/libv4l.mk

@@ -73,6 +73,10 @@ else
 LIBV4L_CONF_OPTS += --disable-v4l-utils
 endif
 
+ifeq ($(BR2_PACKAGE_SDL2_IMAGE),y)
+LIBV4L_DEPENDENCIES += sdl2_image
+endif
+
 LIBV4L_CONF_ENV += LIBS="$(LIBV4L_LIBS)"
 
 $(eval $(autotools-package))