s390/sclp: move pci related commands to separate file

sclp commands only used by the PCI code shouldn't be build for
!CONFIG_PCI. Instead of adding more ifdefs to sclp_cmd.c just
move them to a new file.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>