doc: complete crypto sample command line

doc: complete crypto sample command line

Documentation of some virtual crypto PMDs have a sample command line
to show how to initialize the device on a specific application,
L2fwd-crypto.

This was meant to be used as a reference, but these lines themselves
do not work, as the sample application used required more parameters,
which are added in this commit to have a fully functional example.

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>