ANDROID: dm: Add wrapped key support in dm-default-key

To prevent keys from being compromised if an attacker acquires read
access to kernel memory, some inline encryption hardware supports
protecting the keys in hardware without software having access to or the
ability to set the plaintext keys.  Instead, software only sees "wrapped
keys", which may differ on every boot.  The keys can be initially
generated either by software (in which case they need to be imported to
hardware to be wrapped), or directly by the hardware.

Add support for this type of hardware by allowing keys to be flagged as
hardware-wrapped. When used, dm-default-key will pass the wrapped key
to the inline encryption hardware to encryption metadata. The hardware
will internally unwrap the key and derive the metadata encryption key.

This is a reworked version of a patch which was temporily reverted by
https://android-review.googlesource.com/c/kernel/common/+/1867365, and
which originated from
https://android-review.googlesource.com/c/kernel/common/+/1224286

.

Bug: 147209885
Bug: 160883801
Bug: 160883266
Bug: 160885805

Test: Validate metadata encryption & FBE with wrapped keys.

Change-Id: I38393727bf71e5d20b3c3ac9d2af62a1864a0a82
Signed-off-by: Barani Muthukumaran <bmuthuku@codeaurora.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
(cherry picked from commit 56e1e0a6)