pci: fix checking PCI_REGION_MEM in pci_hose_phys_to_bus()

When converting between PCI bus and phys addresses, a two pass search
was introduced with preference to non-PCI_REGION_SYS_MEMORY regions.
See commit 2d43e873.

However, since PCI_REGION_MEM is defined as 0, the if statement was
always asserted true: ((flags & PCI_REGION_MEM) == PCI_REGION_MEM)

This patch uses PCI_REGION_TYPE bit to check if the region is
PCI_REGION_MEM: ((flags & PCI_REGION_TYPE) == PCI_REGION_MEM)

Signed-off-by: Cheng Gu <chenggu@marvell.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>