dcbnl: more informed return values for new dcbnl routines
dcbnl: more informed return values for new dcbnl routines

More accurate return values for the following (new) dcbnl routines:
dcbnl_getdcbx()
dcbnl_setdcbx()
dcbnl_getfeatcfg()
dcbnl_setfeatcfg()

Signed-off-by: Shmulik Ravid <ffeca5f1c568de7d41a6926e8b352bf8fb58106d@broadcom.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs