net: Fix slip compilation issue with debug option enabled Slip context parameter is not used in hexdump and in few places it is not defined. So CONFIG_SLIP_DEBUG=y throws errors. Change-Id: I73ca26b7d5cd7c3cd532462b5300e25bbdac9511 Signed-off-by: Ravi kumar Veeramally <ravikumar.veeramally@linux.intel.com>