Fixes for latest FFmpeg version when compiling for aarch64 using armasm64

[montoyo]

Hey there, Was trying to build the latest FFmpeg version for ARM64 using MSVC and encountered a few errors regarding libavcodec/aarch64/vc1dsp_neon.S and libavcodec/aarch64/hevcdsp_sao_neon.S. I attempted to fix them by implementing patching for the tbnz and tbx instructions.

Disclaimer: I have no knowledge of perl nor ARM64 assembly, I simply attempted to fix the compiler issues. I thought I'd still create a pull-request, just in case it would help someone 😊

[madebr]

This helped me today with building the asm codecs of dav1d. The SDL project thanks you :)