pti: add missing CONFIG_PCI dependency

allmodconfig compile fails on s390 because of the new PTI driver:

drivers/misc/pti.c:407:3: error: implicit declaration of function 'pci_iounmap'
drivers/misc/pti.c:410:3: error: implicit declaration of function 'pci_release_region'

Add a 'depends on PCI' statement so it doesn't get compiled.

Cc: J Freyensee <james_p_freyensee@linux.intel.com>

Signed-off-by: Tracey Dent <tdent48227@gmail.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>