erspan: set bso bit based on mirrored packet's len

erspan: set bso bit based on mirrored packet's len

Upstream commit:
    Before the patch, the erspan BSO bit (Bad/Short/Oversized) is not
    handled.  BSO has 4 possible values:
      00 --> Good frame with no error, or unknown integrity
      11 --> Payload is a Bad Frame with CRC or Alignment Error
      01 --> Payload is a Short Frame
      10 --> Payload is an Oversized Frame

    Based the short/oversized definitions in RFC1757, the patch sets
    the bso bit based on the mirrored packet's size.

    Reported-by: Xiaoyan Jin <xiaoyanj@vmware.com>
    Signed-off-by: William Tu <u9012063@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: William Tu <u9012063@gmail.com>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: William Tu <u9012063@gmail.com>