app/testpmd: fix descriptor number for Rx queue setup
app/testpmd: fix descriptor number for Rx queue setup

Wrong index used to select descriptor number, causing setting up queue
with wrong number of descriptors.

Fixes: d44f8a485f5d ("app/testpmd: enable per queue configure")

Signed-off-by: Ferruh Yigit <ba8734c3c506d2e3557bd4ac8fdaccd25bdb9aa7@intel.com>
Acked-by: Bernard Iremonger <233eeff376ad0c06f66f06c5522ea3c4feb30d3b@intel.com>

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