ffmpeg: upgrade 6.1.1 -> 6.1.2

ffmpeg: upgrade 6.1.1 -> 6.1.2

ffmpeg_6.1.2 is the newest available stable release for 6.1.
It introduces quite a few bug and CVE fixes, which should help all.

CVEs that are fixed in the upgrade:
CVE-2024-32230
CVE-2024-35366
CVE-2024-36613
CVE-2024-36616
CVE-2024-36617
CVE-2024-36619
CVE-2024-7055

During upgrade it was noticed that the CVE scan doesn't pick up the CVEs as unpatched
(CVE-2025-0518, CVE-2025-22919, CVE-2025-22921, CVE-2025-25473,
CVE-2024-36618, CVE-2024-35369, CVE-2024-35368, CVE-2024-35367,
CVE-2024-35365, CVE-2024-28661, CVE-2023-50007, CVE-2023-49528,
CVE-2023-49501), due to improper versioning in NVD,
they are affecting 6.1.2 and hence we are leaving the patches in.

check the changelog mention below for information about fixes.
changelog: https://git.ffmpeg.org/gitweb/ffmpeg.git/shortlog/n6.1.2

This upgrade fixes CVE's hence remove those patches.
Refresh vulkan_av1_stable_API.patch as per new codebase.

Signed-off-by: Divyanshu Rathore <divyanshurathore2022@gmail.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>