libavcodec: Remove dynamic relocs from aarch64/h264idct_neon.S

libavcodec: Remove dynamic relocs from aarch64/h264idct_neon.S

Some of the assembly functions e.g. ff_h264_idct_dc_add_neon
has code like:
        movrel          x14, X(ff_h264_idct_add_neon)

Linker cannot resolve them fully at link time and emits dynamic
relocations.
Use explicit labels instead so that no dynamic relocations are
needed at all.

This avoids lld complains about text relocations.

For background, see https://crbug.com/917919

Signed-off-by: Manoj Gupta <manojgupta@chromium.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>