tpm xen: drop unneeded chip variable

tpm xen: drop unneeded chip variable

The call that used chip was dropped in 1f0f30e404b3.  Drop the
leftover declaration and initialization.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
OraBug: 26662731

(cherry picked from commit 5cec5bacd37784a1596d2f8fea377212948a0bf4)
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>