vulkanh265dec: fix reference set
StdVideoDecodeH265PictureInfo.flags.IsReference
refers to section 3.132 ITU-T
H.265 specification:
reference picture: A picture that is a short-term reference picture or a long-term reference picture.
GstH265Picture.ref
doesn't reflect this, but we need to query the NAL type of
the processed slice.
This patch fixes the validation layer error
VUID-vkCmdBeginVideoCodingKHR-slotIndex-07239
while using the NVIDIA driver.
Also this MR contains a code-style fix, non-functional, for vulkanh264dec
Edited by Víctor Manuel Jáquez Leal