drivers/i2c/tpm: Add irq_gpio support to tpm.

Grunt (a amd-stoneyridge based platform) uses a GPIO to interface with
the tpm. This change allows devicetree entries to use a irq_gpio entry
to describe the interface with the TPM.

BUG=b:72655090

Change-Id: I08289891408d7176f68eb9c67f7a417a2448c2de
Signed-off-by: Justin TerAvest <teravest@chromium.org>
Reviewed-on: https://review.coreboot.org/23500
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/drivers/i2c/tpm/chip.h

@@ -7,4 +7,5 @@ struct drivers_i2c_tpm_config {
 	unsigned int uid;	/* ACPI _UID */
 	enum i2c_speed speed;	/* Bus speed in Hz, default is I2C_SPEED_FAST */
 	struct acpi_irq irq;	/* Interrupt */
+	struct acpi_gpio irq_gpio;	/* GPIO interrupt */
 };