powerpc/machdep: Define 'compatible' property in ppc_md and use it

Most probe functions do nothing else than checking whether
the machine is compatible to a given string.

Define that string in ppc_md structure and check it directly from
probe_machine() instead of using ppc_md.probe() for that.

Keep checking in ppc_md.probe() only for more complex probing.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/6cb9865d916231c38401ba34ad1a98c249fae135.1676711562.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/machdep.h

@@ -21,6 +21,7 @@ struct pci_host_bridge;
 
 struct machdep_calls {
 	const char	*name;
+	const char	*compatible;
 #ifdef CONFIG_PPC64
 #ifdef CONFIG_PM
 	void		(*iommu_restore)(void);

arch/powerpc/kernel/setup-common.c

@@ -630,14 +630,15 @@ static __init void probe_machine(void)
 	for (machine_id = &__machine_desc_start;
 	     machine_id < &__machine_desc_end;
 	     machine_id++) {
-		DBG("  %s ...", machine_id->name);
+		DBG("  %s ...\n", machine_id->name);
+		if (machine_id->compatible && !of_machine_is_compatible(machine_id->compatible))
+			continue;
 		memcpy(&ppc_md, machine_id, sizeof(struct machdep_calls));
-		if (ppc_md.probe()) {
-			DBG(" match !\n");
+		if (ppc_md.probe && !ppc_md.probe())
+			continue;
+		DBG("   %s match !\n", machine_id->name);
 		break;
 	}
-		DBG("\n");
-	}
 	/* What can we do if we didn't find ? */
 	if (machine_id >= &__machine_desc_end) {
 		pr_err("No suitable machine description found !\n");