package/ffmpeg: bump version to 4.3

package/ffmpeg: bump version to 4.3

Add a patch to fix build without ssse3.

Update the license hash due to various changes since August 2019 [0]:

  - some files were relicensed from GPL-2.0+ to LGPL-2.1+; no impact on
    the licensing information;

  - clarification about the licensing when linked with external
    libraries, which now requires passing --enable-version3; Buildroot
    is not concerned, because it passes --disable-version3;

  - various clarification about applicable licensing terms.

[0] http://git.videolan.org/?p=ffmpeg.git;a=history;f=LICENSE.md;h=613070e1b631a919a74c862f2a75a0f249a631ff;hb=8e12af29d1a3f95c9e952d78354e3c8b1c0431a8

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
[yann.morin.1998@free.fr:
  - fix the SoB order in the patch
  - clarify the impact of the licensing changes
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>