riscv/crc64: add Zbc optimized CRC64 functions

riscv/crc64: add Zbc optimized CRC64 functions

Wire up crc64_be_arch() and crc64_nvme_arch() for 64-bit RISC-V using
crc-clmul-template.h.  This greatly improves the performance of these
CRCs on Zbc-capable CPUs in 64-bit kernels.

These optimized CRC64 functions are not yet supported in 32-bit kernels,
since crc-clmul-template.h assumes that the CRC fits in an unsigned
long.  That implementation limitation could be addressed, but it would
add a fair bit of complexity, so it has been omitted for now.

Tested-by: Björn Töpel <bjorn@rivosinc.com>
Acked-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20250216225530.306980-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>