mmc: host: Set the supported dun size for crypto

Driver need to register the supported data unit number (dun) size
with keyslot manager so that encryption request with unsupported
dun size can fallback to fs or block crypto.

Change-Id: If0b724a80049fb3544a6338345a55bf7d1084127
Signed-off-by: Neeraj Soni <neersoni@codeaurora.org>