compressdev: clarify destination buffer size
compressdev: clarify destination buffer size

Clarify the corner case with incompressible data
whereby the output can actually be greater than the
uncompressed data.

Signed-off-by: Fiona Trahe <7ba562cc372916cd557d0be347608f8b4da4f746@intel.com>
Acked-by: Adam Dybkowski <b636839fd6da8c90d3d28fcb76555ed5d2c5a673@intel.com>
Acked-by: Shally Verma <27e08ff3755965c1c81ca0157f492f83834eddc9@marvell.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk