lib/crypto: riscv/poly1305: Import OpenSSL/CRYPTOGAMS implementation

lib/crypto: riscv/poly1305: Import OpenSSL/CRYPTOGAMS implementation

This is a straight import of the OpenSSL/CRYPTOGAMS Poly1305
implementation for riscv authored by Andy Polyakov.  The file
'poly1305-riscv.pl' is taken straight from
https://github.com/dot-asm/cryptogams commit
5e3fba73576244708a752fa61a8e93e587f271bb.  This patch was tested on
SpacemiT X60, with 2~2.5x improvement over generic implementation.

Signed-off-by: Chunyan Zhang <zhangchunyan@iscas.ac.cn>
Signed-off-by: Zhihang Shao <zhihang.shao.iscas@gmail.com>
[EB: ported to lib/crypto/riscv/]
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250829152513.92459-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>