i386: Misc PCI fixups

Change PCI_REGION_MEMORY to PCI_REGION_SYS_MEMORY (Originally done in
commit ff4e66e9, regressed by commit 6d7f610b)

Cast PCI_ROM_ADDRESS_MASK to u32

Wrap probe_pci_video() call inside #ifdef CONFIG_VIDEO

Change call to pci_find_class() to pci_find_devices(). This is based on a
patch submitted on 1st March 2007 (Patch that fixes the compilation errors
for sc520_cdp board) by mushtaq_k

This patch requires that PCI_VIDEO_VENDOR_ID and PCI_VIDEO_DEVICE_ID be
specified in the board config file.  Dummy values have been added for the
SC520 CDP board to enable compilation, but since I do not have one of these,
I do know what the values should be

Signed-off-by: Graeme Russ <graeme.russ@gmail.com>