smb: client: Add tracepoint for krb5 auth

smb: client: Add tracepoint for krb5 auth

Add tracepoint to help debugging krb5 auth failures.

Example:

$ trace-cmd record -e smb3_kerberos_auth
$ mount.cifs ...
$ trace-cmd report
mount.cifs-1667 [003] .....  5810.668549: smb3_kerberos_auth: vers=2
host=w22-dc1.zelda.test ip=192.168.124.30:445 sec=krb5 uid=0 cruid=0
user=root pid=1667 upcall_target=app err=-126

Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Reviewed-by: David Howells <dhowells@redhat.com>
Cc: Pierguido Lambri <plambri@redhat.com>
Cc: linux-cifs@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>