configure: remove tpm_passthrough & tpm_emulator

This is a left-over from commit 7aaa6a16 "tpm: express dependencies
with Kconfig".

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20190524181411.8599-1-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>