dpdk-cryptodev: improve cryptodev cache ring implementation

dpdk-cryptodev: improve cryptodev cache ring implementation

Sw ring is renamed to the cache ring. This name better reflects the
puropse of this ring. We've introduced push/pop functions, as well as
other utility functions which remove code repetition. Error handlig
is improved: previously in case of an error all frame elements were
marked as bad, now only these for which errors occured have the error
status set.
Unnecessary stats counters have been removed.

Type: improvement
Signed-off-by: Piotr Bronowski <piotrx.bronowski@intel.com>
Change-Id: I2fd42a529ac84ce5ad260611d6b35a861d441c79