build: update assembly variable names for vet

src/pkg/bytes/asm_386.s

src/pkg/bytes/asm_amd64.s

src/pkg/bytes/asm_arm.s

src/pkg/crypto/md5/md5block_386.s

src/pkg/crypto/md5/md5block_amd64.s

src/pkg/crypto/rc4/rc4_386.s

src/pkg/crypto/rc4/rc4_amd64.s

src/pkg/crypto/sha1/sha1block_386.s

src/pkg/crypto/sha1/sha1block_amd64.s

src/pkg/crypto/sha1/sha1block_decl.go

src/pkg/hash/crc32/crc32_amd64.s

src/pkg/math/abs_386.s

src/pkg/math/abs_amd64.s

src/pkg/math/abs_arm.s

src/pkg/math/asin_386.s

src/pkg/math/atan2_386.s

src/pkg/math/atan_386.s

src/pkg/math/big/arith_386.s

src/pkg/math/big/arith_amd64.s

src/pkg/math/big/arith_arm.s