net: Do not set appdata on a cloned packet

Current implementation only considers IP header length while setting
appdata value on a cloned packet. It will give bogus value if original
packet contains extension headers and if extension headers are large
(i.e. more than one fragment). Only consider appdata length from the
original packet.

Signed-off-by: Ravi kumar Veeramally <ravikumar.veeramally@linux.intel.com>