rsa/rsa_pk1.c: remove memcpy calls from RSA_padding_check_PKCS1_type_2.

And make RSAErr call unconditional.

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(cherry picked from commit e875b0cf)

(Merged from https://github.com/openssl/openssl/pull/7735)