xsigo: hard LOCKUP in freeing paths

xsigo: hard LOCKUP in freeing paths

Orabug: 24669507

When path->users becomes zero uVNIC driver starts
cleaning up the Forwarding table entries.

In some corner cases the call is invoked from transmit
function which is in interrupt context and that results
in a hard LOCKUP.

With new changes path->users is decremented in transmit
function to allow cleanup to happen from other thread.
Proper care is taken to avoid race between these
two contexts.

Reported-by: chien yen <chien.yen@oracle.com>
Signed-off-by: Pradeep Gopanapalli <pradeep.gopanapalli@oracle.com>
Reviewed-by: Aravind Kini <aravind.kini@oracle.com>
Reviewed-by: viswa krishnamurthy <viswa.krishnamurthy@oracle.com>
Reviewed-by: Manish Kumar Singh <mk.singh@oracle.com>
Reviewed-by: UmaShankar Tumari Mahabalagiri <umashankar.mahabalagiri@oracle.com>