[patch] multimedia/ffmpeg fix for libvdpau dependency

[Dominic Fandrey]

libvdpau is only a build dependency, even though it is dynamically
linked.

I.e. after running /pkg autoremove/ running ffmpeg failed:
# ffmpeg
Shared object "libvdpau.so.1" not found, required by "ffmpeg"

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Index: multimedia/ffmpeg/Makefile
===================================================================
--- multimedia/ffmpeg/Makefile	(revision 374809)
+++ multimedia/ffmpeg/Makefile	(working copy)
@@ -178,7 +178,7 @@
 VAAPI_CONFIGURE_ENABLE=	vaapi
 
 # vdpau
-VDPAU_BUILD_DEPENDS=	${LOCALBASE}/include/vdpau/vdpau.h:${PORTSDIR}/multimedia/libvdpau
+VDPAU_LIB_DEPENDS=	libvdpau.so:${PORTSDIR}/multimedia/libvdpau
 VDPAU_CONFIGURE_ENABLE=	vdpau
 
 # vo-aacenc