doc: fix crypto perf script guide
doc: fix crypto perf script guide

The guide for using the crypto perf graphing script had some incorrect
indentation, unnecessary blank lines, and a missing argument in one of
the usage examples. These are corrected in this patch.

Fixes: f400e0b82bf1 ("app/crypto-perf: add script to graph perf results")

Signed-off-by: Ciara Power <2dd8f648091a527a3f34edd30b226be01da76a0e@intel.com>
Acked-by: Adam Dybkowski <b636839fd6da8c90d3d28fcb76555ed5d2c5a673@intel.com>

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