x86: add force_hpet boot option

add force_hpet boot option.

(this will be useful to make the forced-enable quirks depend on.)

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/hpet.h b/include/asm-x86/hpet.h
index d4ab6db..4f51519 100644
--- a/include/asm-x86/hpet.h
+++ b/include/asm-x86/hpet.h
@@ -64,6 +64,7 @@
 /* hpet memory map physical address */
 extern unsigned long hpet_address;
 extern unsigned long force_hpet_address;
+extern int hpet_force_user;
 extern int is_hpet_enabled(void);
 extern int hpet_enable(void);
 extern unsigned long hpet_readl(unsigned long a);