Link libatomic on riscv32

Link libatomic on riscv32

GCC toolchains on linux are not able to build libcrypto without linking
to libatomic as it does not have all needed atomics implemented as
intrinsics

Fixes errors like

| ld: ./libcrypto.so: undefined reference to `__atomic_is_lock_free'

CLA: trivial
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22460)