drivers/fsl_pci_init: Fix compile warning

fsl_pci_init.c: In function 'fsl_pci_setup_inbound_windows':
fsl_pci_init.c:122: warning: comparison is always true due to limited range of data type

The check only makes sense if we are CONFIG_PHYS_64BIT

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>