powerpc: mm: add VM_IOREMAP flag to the vmalloc area

Currently, for vmalloc areas with flag VM_IOREMAP set, except of the
specific alignment clamping in __get_vm_area_node(), they will be

 1) Shown as ioremap in /proc/vmallocinfo;

 2) Ignored by /proc/kcore reading via vread()

So for the io mapping in ioremap_phb() of ppc, we should set VM_IOREMAP in
flag to make it handled correctly as above.

Link: https://lkml.kernel.org/r/20230206084020.174506-7-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Dan Carpenter <error27@gmail.com>
Cc: Stephen Brennan <stephen.s.brennan@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/powerpc/kernel/pci_64.c

@@ -132,7 +132,7 @@ void __iomem *ioremap_phb(phys_addr_t paddr, unsigned long size)
 	 * address decoding but I'd rather not deal with those outside of the
 	 * reserved 64K legacy region.
 	 */
-	area = __get_vm_area_caller(size, 0, PHB_IO_BASE, PHB_IO_END,
+	area = __get_vm_area_caller(size, VM_IOREMAP, PHB_IO_BASE, PHB_IO_END,
 				    __builtin_return_address(0));
 	if (!area)
 		return NULL;