package/mesa3d: add xlib_libXv dependency to mesa3d xvmc

package/mesa3d: add xlib_libXv dependency to mesa3d xvmc

From [1]

  "Prior to xvmc 1.0.12 libxvmc incorrectly required libxv, but that
   was fixed. This results in compilation failures for the gallium
   xvmc tracker and tools. This patch fixes that by explicitly linking
   to libxv."

Add xlib_libXv dependency to mesa3d when BR2_PACKAGE_MESA3D_XVMC is set.

[1] https://cgit.freedesktop.org/mesa/mesa/commit/?id=e456a053c3d6ec4f3d4581edcad05c72dfdaa407

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Bernd Kuhls <bernd.kuhls@t-online.de>
Tested-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>