ffmpeg: fix assembling with binutils v2.41

ffmpeg: fix assembling with binutils v2.41

fix addresses issue when building ffmpeg with binutils v2.41
that is documented here: https://trac.ffmpeg.org/ticket/10405

Issue about build failure is available here:
https://github.com/openwrt/packages/issues/22170

Remarks:
Patch is merged to ffmpeg upstream and will be included in
next release of ffmpeg, so patch applies only to current
version and is removed when package is updated to next
version of ffmpeg.

Signed-off-by: Oskari Rauta <oskari.rauta@gmail.com>
Co-authored-by: Josef Schlehofer <pepe.schlehofer@gmail.com>