arc: Build Recipients for EC P-256 For ECDH-HKDF calculation, the recipient derivation assumes X25519 key. For ChromeOS, we are using EC P-256 key. This CL changes the derivation of Recipients accordingly. BUG=b:381769014 TEST=emerge-brya chromeos-base/arc-keymint TEST=cros_workon_make --board=brya chromeos-base/arc-keymint --test Change-Id: Iffe1b92ed33b1e2d20756f48001bdc9a428f6ef0 Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/keymaster/+/6061721 Reviewed-by: Yao Li <[email protected]> Tested-by: Vaibhav Raheja <[email protected]> Commit-Queue: Vaibhav Raheja <[email protected]>