streebog: improve `adc` (#587) #612

Job	Run time
minimal-versions / minimal-versions	1m 5s
set-msrv / set-msrv	5s
test (1.71.0)	50s
build (1.71.0, thumbv7em-none-eabi)	20s
test (stable)	31s
build (1.71.0, wasm32-unknown-unknown)	23s
build (stable, thumbv7em-none-eabi)	13s
build (stable, wasm32-unknown-unknown)	25s
	3m 52s

Provide feedback