drivers/i2c/tpm: Add support for generating ACPI table

Add code to generate an ACPI descriptor for an I2C TPM based
on the device as described in devicetree.cb.

This currently requires the devicetree to provide the HID,
since we don't currently talk to the TPM in ramstage and I
didn't want to add yet another init path for it here.

This was tested on a reef board to ensure that the device
is described properly in the SSDT.

Change-Id: I43d7f6192f48e99a4074baa4e52f0a9ee554a250
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/16397
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/drivers/i2c/tpm/chip.h

@@ -0,0 +1,10 @@
+#include <arch/acpi_device.h>
+#include <device/i2c.h>
+
+struct drivers_i2c_tpm_config {
+	const char *hid;	/* ACPI _HID (required) */
+	const char *desc;	/* Device Description */
+	unsigned uid;		/* ACPI _UID */
+	enum i2c_speed speed;	/* Bus speed in Hz, default is I2C_SPEED_FAST */
+	struct acpi_irq irq;	/* Interrupt */
+};