ethdev: support WRED thresholds in bytes

ethdev: support WRED thresholds in bytes

WRED thresholds can be specified in bytes if the TM leaf
node supports it. Also extend WRED thresholds to 32 bits from 16.

TM capability (port/level/queue) fields cman_wred_packet_mode_supported and
cman_wred_byte_mode_supported, when non-zero, indicate support for WRED
thresholds in packets and bytes respectively.

The packet_mode member of struct rte_tm_wred_params, when non-zero,
indicates that the min and max thresholds are specified in
packets and when zero, indicates that the min and max thresholds
are specified in bytes.

Signed-off-by: Nikhil Rao <nikhil.rao@intel.com>