[POWERPC] Fix backwards ? : when printing machine type

Looks like someone got this backwards, highlighting the perils of the
? : !!! :)
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

arch/powerpc/kernel/traps.c

@@ -153,7 +153,7 @@ int die(const char *str, struct pt_regs *regs, long err)
 #ifdef CONFIG_NUMA
 		printk("NUMA ");
 #endif
-		printk("%s\n", ppc_md.name ? "" : ppc_md.name);
+		printk("%s\n", ppc_md.name ? ppc_md.name : "");
 
 		print_modules();
 		show_regs(regs);