pseries: Don't try to munmap() a malloc()ed TCE table

For the pseries machine, TCE (IOMMU) tables can either be directly
malloc()ed in qemu or, when running on a KVM which supports it, mmap()ed
from a KVM ioctl.  The latter option is used when available, because it
allows the (frequent bottlenext) H_PUT_TCE hypercall to be KVM accelerated.
However, even when KVM is persent, TCE acceleration is not always possible.
Only KVM HV supports this ioctl(), not KVM PR, or the kernel could run out
of contiguous memory to allocate the new table.  In this case we need to
fall back on the malloc()ed table.

When a device is removed, and we need to remove the TCE table, we need to
either munmap() or free() the table as appropriate for how it was
allocated.  The code is supposed to do that, but we buggily fail to
initialize the tcet->fd variable in the malloc() case, which is used as a
flag to determine which is the right choice.

This patch fixes the bug, and cleans up error messages relating to this
path while we're at it.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>
