s390/pci: remove iomap sanity checks

s390/pci: remove iomap sanity checks

BugLink: http://bugs.launchpad.net/bugs/1558624
Since each iomap_entry handles only one bar of one pci function
(even when disjunct ranges of a bar are mapped) the sanity check
in pci_iomap_range is not needed and can be removed.

Also convert the remaining BUG_ONs to WARN_ONs.

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 f5e44f82c1848d8e55fb0061308f14c0884e5483)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>