staging: ccree: use array for double buffer

The ccree hash code is using a double buffer to hold data
for processing but manages the buffers and their associated
data count in two separate fields and uses a predicate to
chose which to use.

Move to using a proper 2 members array for a much cleaner code.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>