PCI: eliminate double kfree in intel-iommu initialization

The destination of goto error also does a kfree(g_iommus), so it is not
correct to do one here.

This was found using Coccinelle (http://www.emn.fr/x-info/coccinelle/

).

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>