i40e: Remove function i40e_update_dcb_config()

This patch removes function i40e_update_dcb_config(). Instead of
i40e_update_dcb_config() we use i40e_init_dcb(), which implements the
correct NVM read.

Signed-off-by: Grzegorz Siwik <grzegorz.siwik@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>