[PATCH] USB: usb-net: removes redundant return

removes all redundant collecting of the return value from
get/set_registers() and suchlike.  can't remember who put all of those
some time ago, but they doesn't make any sense to me.  where needed only
a few references remained;

Signed-off-by: Petko Manolov <petkan@nucleusys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>