Support for a new watchdog action inject-nmi
    
    This patch provides support for a new watchdog action "inject-nmi" which
    allows to define an inject of a non-maskable interrupt into a guest.
    
    Signed-off-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
    Reviewed-by: Daniel Hansel <daniel.hansel@linux.vnet.ibm.com>
    Reviewed-by: Stefan Zimmermann <stzi@linux.vnet.ibm.com>
    Reviewed-by: Tony Krowiak <akrowiak@linux.vnet.ibm.com>