mtd/nand/r852: fix build for CONFIG_PM=n

Fix r852 build for the case of CONFIG_PM=n.

drivers/mtd/nand/r852.c:1039: error: implicit declaration of function 'pci_prepare_to_sleep'
drivers/mtd/nand/r852.c:1048: error: implicit declaration of function 'pci_back_from_sleep'

This patch leaves r852_pm_ops untouched.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>