vlc: correct sdl_image dependency name

Fixes http://autobuild.buildroot.net/results/7e8/7e85b79612a46df2eee0278703f54d872da72ed5/

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/vlc/vlc.mk

@@ -214,7 +214,7 @@ endif
 
 ifeq ($(BR2_PACKAGE_SDL_IMAGE),y)
 VLC_CONF_OPT += --enable-sdl-image
-VLC_DEPENDENCIES += sdl-image
+VLC_DEPENDENCIES += sdl_image
 else
 VLC_CONF_OPT += --disable-sdl-image
 endif