Add DEBUG_TPM option to Debugging menu

instead of having to edit the source code of tpm.c

Change-Id: I519d9ada14dd383e668a2da4219e5373a24c7c3d
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: http://review.coreboot.org/757
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/Kconfig

@@ -862,6 +862,13 @@ config X86EMU_DEBUG_IO
 
 	  If unsure, say N.
 
+config DEBUG_TPM
+	bool "Output verbose TPM debug messages"
+	default n
+	depends on TPM
+	help
+	  This option enables additional TPM related debug messages.
+
 config LLSHELL
 	bool "Built-in low-level shell"
 	default n