package/ffmpeg: bump version to 3.4.1

package/ffmpeg: bump version to 3.4.1

Configure options for libnut & libschroedinger were removed:
http://git.videolan.org/?p=ffmpeg.git;a=commit;h=a3deeaade32db5a1b736b8d3365e52254f3fa6ac
http://git.videolan.org/?p=ffmpeg.git;a=commit;h=220b24c7c97dc033ceab1510549f66d0e7b52ef1

Upstream now prefers NASM assembler over YASM:
http://git.videolan.org/?p=ffmpeg.git;a=commit;h=4f9297ac3b39098547863d28fbc8d2a906d5be49

Added configure options for alsa support:
http://git.videolan.org/?p=ffmpeg.git;a=commitdiff;h=b447629093d75f18d0a8fc44ec768022322b2182

Added configure options for libiconv:
http://git.videolan.org/?p=ffmpeg.git;a=commitdiff;h=fe9c85e4e2650dc9537b54b1eabb4f9be7b628ed

Added license hashes.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>