ixgbe: Correct flag values set by ixgbe_fix_features

ixgbe: Correct flag values set by ixgbe_fix_features

This patch replaces the variable name data with the variable name features
for ixgbe_fix_features and ixgbe_set_features.  This helps to make some
issues more obvious such as the fact that we were disabling Rx VLAN tag
stripping when we should have been forcing it to be enabled when DCB is
enabled.

In addition there was deprecated code present that was disabling the LRO
flag if we had the itr value set too low.  I have updated this logic so
that we will now allow the LRO flag to be set, but will not enable RSC
until the rx-usecs value is high enough to allow enough time for Rx packet
coalescing.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>