Small improvements made to the compressdev programmer's guide.
This includes rephrasing some sentences, fixing grammar,
and aligning formatting.
Fixes: a584d3bea902 ("doc: add compressdev library guide")
Fixes: f7095d41bba6 ("doc: clarify data plane error handling in compressdev")
Cc: stable@dpdk.org
Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Fan Zhang <roy.fan.zhang@intel.com>