Staging: sxg: Fix memory leak in case of allocation failure

* Fix a memory leak if allocation of skb fails in sxg_fill_descriptor_block.
  In sxg_fill_descriptor_block(), if allocation of skb failed in loop,
  we just came out shouting. This rollbacks all the successful operation
  before skb allocation fails and then returns.

Signed-off-by: LinSysSoft Sahara Team <saharaproj@linsyssoft.com>
Signed-off-by: Mithlesh Thukral <mithlesh@linsyssoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>