xen/grant-table: Refactor gnttab_init

We have this odd scenario of where for PV paths we take a shortcut
but for the HVM paths we first ioremap xen_hvm_resume_frames, then
assign it to gnttab_shared.addr. This is needed because gnttab_map
uses gnttab_shared.addr.

Instead of having:
	if (pv)
		return gnttab_map
	if (hvm)
		...

	gnttab_map

Lets move the HVM part before the gnttab_map and remove the
first call to gnttab_map.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: NDavid Vrabel <david.vrabel@citrix.com>
Acked-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>

drivers/xen/grant-table.c

@@ -1173,10 +1173,7 @@ static int gnttab_setup(void)
 	if (max_nr_gframes < nr_grant_frames)
 		return -ENOSYS;
 
-	if (xen_pv_domain())
-		return gnttab_map(0, nr_grant_frames - 1);
-
-	if (gnttab_shared.addr == NULL) {
+	if (xen_feature(XENFEAT_auto_translated_physmap) && gnttab_shared.addr == NULL) {
 		gnttab_shared.addr = xen_remap(xen_hvm_resume_frames,
 						PAGE_SIZE * max_nr_gframes);
 		if (gnttab_shared.addr == NULL) {
@@ -1185,10 +1182,7 @@ static int gnttab_setup(void)
 			return -ENOMEM;
 		}
 	}
-
-	gnttab_map(0, nr_grant_frames - 1);
-
-	return 0;
+	return gnttab_map(0, nr_grant_frames - 1);
 }
 
 int gnttab_resume(void)