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/intel-iommu.c b/drivers/pci/intel-iommu.c
index 2dc72a6..833509b 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -37,8 +37,8 @@
 #include <linux/iommu.h>
 #include <linux/intel-iommu.h>
 #include <linux/sysdev.h>
+#include <linux/tboot.h>
 #include <asm/cacheflush.h>
-#include <asm/tboot.h>
 #include <asm/iommu.h>
 #include "pci.h"