package/ti-sgx-km: properly handle legacy for renamed options

Commit b54c5464 (ti-sgx-km: rename options to have proper prefix)
forgot to add defaults from legacy options, and notices in
Config.in.legacy that legacy options are still referenced in the
package itself.

Reported-by: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>