ethdev: add return code to device info get function

ethdev: add return code to device info get function

Change rte_eth_dev_info_get() return value from void to int and return
negative errno values in case of error conditions.
Modify rte_eth_dev_info_get() usage across the ethdev according
to new return type.

Signed-off-by: Ivan Ilchenko <ivan.ilchenko@oktetlabs.ru>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>