[PATCH] powerpc: Fix machine detection in prom_init.c

In e8222502 the detection of machine types
in prom_init broke for some machines. We should be checking /device_type
instead of /model. This should make Power3 and Power4 boot again. Haven't
been able to test this.  We also need to relocate before comparing.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/kernel/prom_init.c

@@ -1528,12 +1528,11 @@ static int __init prom_find_machine_type(void)
 	 *    non-IBM designs !
 	 *  - it has /rtas
 	 */
-	len = prom_getprop(_prom->root, "model",
+	len = prom_getprop(_prom->root, "device_type",
 			   compat, sizeof(compat)-1);
 	if (len <= 0)
 		return PLATFORM_GENERIC;
-	compat[len] = 0;
-	if (strcmp(compat, "chrp"))
+	if (strncmp(compat, RELOC("chrp"), 4))
 		return PLATFORM_GENERIC;
 
 	/* Default to pSeries. We need to know if we are running LPAR */