net/i40e/base: fix Tx descriptors number

net/i40e/base: fix Tx descriptors number

The existing driver allows setting the number of TX descriptors
to the value that is indivisible by 32. This is not properly
supported by x710 hardware. The patch limits the number of TX
descriptors to the whole value of 32.

Fixes: 8db9e2a1b232 ("i40e: base driver")
Cc: stable@dpdk.org
Signed-off-by: Doug Dziggel <douglas.a.dziggel@intel.com>
Signed-off-by: Dariusz Chaberski <dariuszx.chaberski@intel.com>
Signed-off-by: Xiaolong Ye <xiaolong.ye@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>
Acked-by: Beilei Xing <beilei.xing@intel.com>