Bring back support for opencv

opencv support was disabled[1] a long time ago because ffmpeg failed
to build with it. opencv 3.x does not support C compilation mode[2]
anymore, and ffmpeg uses only C. There is no ffmpeg interest[3] in
compiling opencv in C++ mode, so opencv2 must be used here.

References
----------
[1] https://aur.archlinux.org/cgit/aur.git/commit/?h=ffmpeg-full&id=5d72306579c20bc36ff7c6ff1005b168e3b263de
[2] https://github.com/opencv/opencv/issues/10963
[3] https://trac.ffmpeg.org/ticket/7059

.SRCINFO

@@ -1,7 +1,7 @@
 pkgbase = ffmpeg-full
 	pkgdesc = Complete solution to record, convert and stream audio and video (all possible features including libfdk-aac)
 	pkgver = 6.1
-	pkgrel = 3
+	pkgrel = 4
 	url = https://www.ffmpeg.org/
 	arch = x86_64
 	license = custom: nonfree and unredistributable
@@ -84,6 +84,7 @@ pkgbase = ffmpeg-full
 	depends = onevpl-intel-gpu
 	depends = openal
 	depends = opencore-amr
+	depends = opencv2
 	depends = openh264
 	depends = openjpeg2
 	depends = openvino