[PATCH] fix the subarch build again after ACPI breakage

The patch to check "maxcpus=N" early broke by putting maxcpus (a
variable which is only exported by mpparse.c) into
parse_cmdline_early().

The fix is to make it depend on the correct CONFIG_ option. 

In the subarchitectures:

CONFIG_X86_SMP is the one that means "I want standard x86 smp code" and
that's what this should depend on.

arch/i386/kernel/setup.c

@@ -560,7 +560,7 @@ static void __init parse_cmdline_early (char ** cmdline_p)
 			}
 		}
 
-#ifdef  CONFIG_SMP
+#ifdef  CONFIG_X86_SMP
 		/*
 		 * If the BIOS enumerates physical processors before logical,
 		 * maxcpus=N at enumeration-time can be used to disable HT.