net/softnic: fix memory leak in arguments parsing

net/softnic: fix memory leak in arguments parsing

In function pmd_parse_args(), firmware path is duplicated from device
arguments as character string, but is never freed, which cause memory
leak.

This patch changes the type of firmware member of struct pmd_params to
character array, to make memory resource release unnecessary, and
changes the type of name member to character array, to keep the
consistency of character string handling in struct pmd_params.

Fixes: 7e68bc20f8c8 ("net/softnic: restructure")
Cc: stable@dpdk.org
Signed-off-by: Dapeng Yu <dapengx.yu@intel.com>
Acked-by: Jasvinder Singh <jasvinder.singh@intel.com>