contrib: ffmpeg: enable thumb
contrib: ffmpeg: enable thumb

Depends on --enable-small and HAVE_NEON
If we use NEON, we assume at least cortex-a8 CPU which means thumb2 is supported

jomanmuk/vlc-2.1,vlc-mirror/vlc,krichter722/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,vlc-mirror/vlc-2.1,krichter722/vlc,shyamalschandra/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,krichter722/vlc,vlc-mirror/vlc,xkfz007/vlc,vlc-mirror/vlc-2.1,krichter722/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc,vlc-mirror/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,xkfz007/vlc,krichter722/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,shyamalschandra/vlc,shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc-2.1,krichter722/vlc,vlc-mirror/vlc-2.1,xkfz007/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,xkfz007/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,vlc-mirror/vlc,xkfz007/vlc,krichter722/vlc,xkfz007/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2