ffmpeg: Fix build on mips

ffmpeg: Fix build on mips

configure is not able to decode, right options to compiler, it needs to
be set according to default tune manually. Fixes build issue on mips
e.g.

 {standard input}: Assembler messages:
| {standard input}:2162: Error: opcode not supported on this processor: mips32r2 (mips32r2) `dmult $22,$22'
| {standard input}:2164: Error: opcode not supported on this processor: mips32r2 (mips32r2) `dsrl $5,$5,32'
| make: *** [/mnt/b/yoe/master/build/tmp/work/mips32r2-yoe-linux/ffmpeg/4.4-r0/ffmpeg-4.4/ffbuild/common.mak:67: libavcodec/aptxenc.o] Error 1

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>