libcrypto: build nistp* on all little-endian 64-bit targets

libcrypto intends to provide these routines on little-endian 64-bit
targets. This was previously done by including them in the ASM_aarch64
and ASM_amd64 blocks in the Makefile, but this excluded powerpc64le and
riscv64.

Reported by: ci.freebsd.org
Reviewed by: jrtc27
Fixes: b077aed33b7b ("Merge OpenSSL 3.0.9")
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D40749