package/tpm2-tss: force libopenssl as openssl provider

package/tpm2-tss: force libopenssl as openssl provider

Select BR2_PACKAGE_OPENSSL_FORCE_LIBOPENSSL and drop the patch to
compile with libressl.

The discussion with the tpm2-tss developers led to the conclusion that
libressl lacks some required functionalities. Quoting Andreas Fuchs[1]:
"LibreSSL does not support OAEP-mode with labels at all, even though the
internal OAEP-padding-function includes the parameters already. [...]
Further, the internal OAEP-padding-function does not support variable
hash algs, but staticly uses SHA1."

Notice that there will NOT be an option to use libgcrypt. OpenSSL will
soon become the default ESAPI crypto backend to prevent the problem of
forcing applications to link against both libgcrypt and libssl[2].

1. https://github.com/tpm2-software/tpm2-tss/pull/1207#issuecomment-440217659
2. https://github.com/tpm2-software/tpm2-tss/issues/1169

Signed-off-by: Carlos Santos <casantos@datacom.com.br>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>