crypto: asym_tpm: correct zero out potential secrets

commit f93274ef upstream.

The function derive_pub_key() should be calling memzero_explicit()
instead of memset() in case the complier decides to optimize away the
call to memset() because it "knows" no one is going to touch the memory
anymore.

Cc: stable <stable@vger.kernel.org>
Reported-by: Ilil Blum Shem-Tov <ilil.blum.shem-tov@intel.com>
Tested-by: Ilil Blum Shem-Tov <ilil.blum.shem-tov@intel.com>
Link: https://lore.kernel.org/r/X8ns4AfwjKudpyfe@kroah.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>