staging: Delete if_strip.h

Commit f80a3f62 ("Staging: strip: delete
the driver") left if_strip.h unused: nothing in the tree includes it
anymore. It is still exported, but since nothing in the kernel uses
struct MetricomAddress, that seems pointless. Delete this header too.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>