s390/pci: fix use after free in dma_init

s390/pci: fix use after free in dma_init

BugLink: http://bugs.launchpad.net/bugs/1584828
After a failure during registration of the dma_table (because of the
function being in error state) we free its memory but don't reset the
associated pointer to zero.

When we then receive a notification from firmware (about the function
being in error state) we'll try to walk and free the dma_table again.

Fix this by resetting the dma_table pointer. In addition to that make
sure that we free the iommu_bitmap when appropriate.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
(cherry picked from commit dba599091c191d209b1499511a524ad9657c0e5a)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>