curve448: Rename arch_ref64 to arch_64

Signed-off-by: Amitay Isaacs <amitay@ozlabs.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14784)

diff --git a/crypto/ec/curve448/arch_ref64/arch_intrinsics.h b/crypto/ec/curve448/arch_64/arch_intrinsics.h
similarity index 100%
rename from crypto/ec/curve448/arch_ref64/arch_intrinsics.h
rename to crypto/ec/curve448/arch_64/arch_intrinsics.h

diff --git a/crypto/ec/curve448/arch_ref64/f_impl.c b/crypto/ec/curve448/arch_64/f_impl.c
similarity index 100%
rename from crypto/ec/curve448/arch_ref64/f_impl.c
rename to crypto/ec/curve448/arch_64/f_impl.c

diff --git a/crypto/ec/curve448/arch_ref64/f_impl.h b/crypto/ec/curve448/arch_64/f_impl.h
similarity index 100%
rename from crypto/ec/curve448/arch_ref64/f_impl.h
rename to crypto/ec/curve448/arch_64/f_impl.h