Use BoringSSL accessors to set up EVP_PKEY.

Constructing an RSA object is sadly a bit tedious, but that's the API
OpenSSL came up with. While I'm here, switch an EVP_PKEY_get1_RSA to
EVP_PKEY_get0_RSA; we can avoid an unnecessary refcount bump.

Test: mm
Change-Id: I8b368ea1efa71e3f8b3cd0c734c1cdd0f2c964e5
1 file changed