x86: mtrr fix debug boot parameter

while looking at:

  http://bugzilla.kernel.org/show_bug.cgi?id=11541

I realized that the mtrr.show param cannot work, because
the code is processed much too early.

This patch:
 - Declares mtrr.show as early_param
 - Stays consistent with the previous param (which I doubt
   that it ever worked), so mtrr.show=1 would still work
 - Declares mtrr_show as initdata
Signed-off-by: NThomas Renninger <trenn@suse.de>
Acked-by: NJan Beulich <jbeulich@novell.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/mtrr/generic.c

@@ -33,11 +33,13 @@ u64 mtrr_tom2;
 struct mtrr_state_type mtrr_state = {};
 EXPORT_SYMBOL_GPL(mtrr_state);
 
-#undef MODULE_PARAM_PREFIX
-#define MODULE_PARAM_PREFIX "mtrr."
-
-static int mtrr_show;
-module_param_named(show, mtrr_show, bool, 0);
+static int __initdata mtrr_show;
+static int __init mtrr_debug(char *opt)
+{
+	mtrr_show = 1;
+	return 0;
+}
+early_param("mtrr.show", mtrr_debug);
 
 /*
  * Returns the effective MTRR type for the region