crypto: x86/poly1305 - emit does base conversion itself

The emit code does optional base conversion itself in assembly, so we
don't need to do that here. Also, neither one of these functions uses
simd instructions, so checking for that doesn't make sense either.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>