app/testpmd: add --portlist option

app/testpmd: add --portlist option

In current version, we are setting the ports
using portmask. With portmask, we can use only
up to 64 ports. This portlist option enables the user
to use more than 64 ports.
Now we can specify the ports in 2 different ways
 - Using portmask (-p [0x]nnn): mask must be in hex format
 - Using portlist in the following format
 --portlist <p1>[-p2][,p3[-p4],...]

 --portmask 0x2 is same as --portlist 1
 --portmask 0x3 is same as --portlist 0-1

Signed-off-by: Hariprasad Govindharajan <hariprasad.govindharajan@intel.com>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
Reviewed-by: Herakliusz Lipiec <herakliusz.lipiec@intel.com>