Handle operations larger than will fit in the buffer we allocate, by processing in a loop.  And bump the size of this buffer (32KB taken by the driver shouldn't be a problem).
Handle operations larger than will fit in the buffer we allocate,
by processing in a loop.  And bump the size of this buffer (32KB
taken by the driver shouldn't be a problem).

Also reduce the places we hard-code the AES block size of 16.

Still disabled (doing more testing), but I want to commit before
the aged hard disk I have in the system here dies.

(This commit from the Geode system with the AES enabled.)

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars