security: pfe: Add capability to process encryption keys of different sizes

With system using both hardware keymanager and secure world to encrypt
the userdata we need to support different encryption key lengths since
different hardware can use any one of the mechanism to generate key or
there can be use case where same target would use different mechanism
to generate the keys for different aosp images.

Change-Id: Ieaf865b4aae935906c75c93383571e813d247395
Signed-off-by: Neeraj Soni <neersoni@codeaurora.org>