Use accessors instead of reaching into the RSA struct am: eedfb29cdb am: 676444f63d am: 1a9a8fe32a am: 5e21eb91fc am: 6a91e5f2d5

Original change: https://android-review.googlesource.com/c/platform/external/vboot_reference/+/2569310

Change-Id: Id583d58c8e2377c63da50e4866838db92761ac0c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>