sha2: Add inline-asm backend for LoongArch64 targets

[heiher]

Tests

default features

$ cargo test
running 8 tests
test sha224_main ... ok
test sha256_main ... ok
test sha512_224_main ... ok
test sha384_main ... ok
test sha512_256_main ... ok
test sha512_main ... ok
test sha512_rand ... ok
test sha256_rand ... ok

test result: ok. 8 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.11s

loongarch64_asm feature

$ cargo test -F loongarch64_asm
running 8 tests
test sha224_main ... ok
test sha384_main ... ok
test sha256_main ... ok
test sha512_224_main ... ok
test sha512_256_main ... ok
test sha512_main ... ok
test sha512_rand ... ok
test sha256_rand ... ok

test result: ok. 8 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.09s

Bench

Without this patch

test sha256_10    ... bench:          59 ns/iter (+/- 0) = 169 MB/s
test sha256_100   ... bench:         569 ns/iter (+/- 1) = 175 MB/s
test sha256_1000  ... bench:       5,068 ns/iter (+/- 3) = 197 MB/s
test sha256_10000 ... bench:      50,033 ns/iter (+/- 26) = 199 MB/s
test sha512_10    ... bench:          42 ns/iter (+/- 0) = 238 MB/s
test sha512_100   ... bench:         402 ns/iter (+/- 0) = 248 MB/s
test sha512_1000  ... bench:       3,613 ns/iter (+/- 2) = 276 MB/s
test sha512_10000 ... bench:      35,465 ns/iter (+/- 22) = 281 MB/s

With this patch

test sha256_10    ... bench:          52 ns/iter (+/- 0) = 192 MB/s
test sha256_100   ... bench:         498 ns/iter (+/- 1) = 200 MB/s
test sha256_1000  ... bench:       4,517 ns/iter (+/- 5) = 221 MB/s
test sha256_10000 ... bench:      44,695 ns/iter (+/- 23) = 223 MB/s
test sha512_10    ... bench:          33 ns/iter (+/- 0) = 303 MB/s
test sha512_100   ... bench:         319 ns/iter (+/- 0) = 313 MB/s
test sha512_1000  ... bench:       2,871 ns/iter (+/- 0) = 348 MB/s
test sha512_10000 ... bench:      28,302 ns/iter (+/- 5) = 353 MB/s