Remove duplicate code from inherent DecodedYUV impl. #181

Job	Run time
test (nasm, i686-unknown-linux-gnu)	1m 14s
test (nasm, x86_64-unknown-linux-gnu)	59s
test (nasm, armv7-unknown-linux-gnueabihf)	1m 20s
test (nasm, x86_64-apple-darwin)	55s
test (nasm, aarch64-apple-darwin)	58s
test (nasm, i686-pc-windows-msvc)	3m 56s
test (nasm, x86_64-pc-windows-msvc)	3m 18s
test (nasm, aarch64-pc-windows-msvc)	1m 58s
test (no-nasm, i686-unknown-linux-gnu)	1m 1s
test (no-nasm, x86_64-unknown-linux-gnu)	59s
test (no-nasm, armv7-unknown-linux-gnueabihf)	1m 0s
test (no-nasm, x86_64-apple-darwin)	1m 11s
test (no-nasm, aarch64-apple-darwin)	2m 14s
test (no-nasm, i686-pc-windows-msvc)	4m 37s
test (no-nasm, x86_64-pc-windows-msvc)	2m 27s
test (no-nasm, aarch64-pc-windows-msvc)	2m 39s
test (aarch64-unknown-linux-gnu, ubuntu-latest, gcc-aarch64-linux-gnu g++-aarch64-linux-gnu, true)	1m 6s
	31m 52s

Provide feedback