zephyr: Fix image encryption configuration for mbedTLS.

Add a few missing Kconfig options.

Note: This PR has been modified from the upstream commit due to
a merge failure from other changes that are not being brought into
Zephyr 3.7

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>
(cherry picked from commit 96b70086)