vdpau: Fix wrong calloc sizeof argument.
Fix warning reported by Coverity Scan.
Wrong sizeof argument (SIZEOF_MISMATCH)
suspicious_sizeof: Passing argument 3544UL (sizeof
(vlVdpPresentationQueue)) to function calloc that returns a pointer of
type vlVdpPresentationQueueTarget * is suspicious because a multiple of
sizeof (vlVdpPresentationQueueTarget) /*16*/ is expected.
Fixes: 65fe0866aec7 ("vl: implemented a few functions and made stubs to get mplayer running")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>