Log Message:
multimedia/dav1d: Update to 1.5.1

Changelog:
Changes for 1.5.1 'Sonic':
--------------------------

1.5.1 is a minor release of dav1d, focusing on optimizations and stack reduction:

 - Rewrite of the looprestoration (SGR, wiener) to reduce stack usage
 - Rewrite of {put,prep}_scaled functions

Now, the required stack space for dav1d should be: 62 KB on x86_64 and
58KB on arm and aarch64.

 - Improvements on the SSSE3 SGR
 - Improvements on ARM32/ARM64 looprestoration optimizations
 - RISC-V: blend optimizations for high bitdepth
 - Power9: blend optimizations for 8bpc
 - Port RISC-V to POSIX/non-Linux OS
 - AArch64: Add Neon implementation of load_tmvs
 - Fix a rare, but possible deadlock, in flush()