x86, intel_txt: clean up the impact on generic code, unbreak non-x86

Move tboot.h from asm to linux to fix the build errors of intel_txt
patch on non-X86 platforms. Remove the tboot code from generic code
init/main.c and kernel/cpu.c.

Signed-off-by: Shane Wang <shane.wang@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index 0cbc5fd..ab99783 100644
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -33,7 +33,7 @@
 #include <linux/timer.h>
 #include <linux/irq.h>
 #include <linux/interrupt.h>
-#include <asm/tboot.h>
+#include <linux/tboot.h>
 
 #undef PREFIX
 #define PREFIX "DMAR:"