cllc: simplify/fix swapped data buffer allocation.

Using the malloc variant avoids pointless memcpy on size
increase and simplifies handling allocation failure.
Also change code to ensure that allocation, bswap and bitstream
reader all use the same size, even when the packet size is odd
for example.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>