They don't modify AVCodec, no needs to call it at register. They will be
wasteful if these codecs are unused. Instead, call static data initialization
at codecs' init.

Benchmark:
old: 51281340 decicycles in avcodec_register_all,       1 runs,      0 skips
new:  6738960 decicycles in avcodec_register_all,       1 runs,      0 skips
Reviewed-by: wm4 <nfxjfg@googlemail.com>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Muhammad Faiz <mfcc64@gmail.com>