[IA64] allow WB /sys/.../legacy_mem mmaps

Allow cacheable mmaps of legacy_mem if WB access is supported for the region.
The "legacy_mem" file often contains a shadow option ROM, and some versions of
X depend on this.

Tim Yamin <plasm@roo.me.uk> reported that this change fixes X on a Dell
PowerEdge 3250.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/pci/pci.c

@@ -659,8 +659,6 @@ pci_mmap_legacy_page_range(struct pci_bus *bus, struct vm_area_struct *vma)
 		return -EINVAL;
 	prot = phys_mem_access_prot(NULL, vma->vm_pgoff, size,
 				    vma->vm_page_prot);
-	if (pgprot_val(prot) != pgprot_val(pgprot_noncached(vma->vm_page_prot)))
-		return -EINVAL;
 
 	addr = pci_get_legacy_mem(bus);
 	if (IS_ERR(addr))