CHROMIUM: Device driver for TPM over virtio

This CL adds a tpm_virtio TPM driver. TPM commands are sent over virtio
to the hypervisor during a TPM send operation and responses are received
over the same virtio queue during a recv operation.

Design doc: go/vtpm-for-glinux

BUG=chromium:911799
TEST=run TPM playground program inside crosvm

Change-Id: Ib85892189fee0be5b34c957caf59dedf5a46ff83
Signed-off-by: David Tolnay <dtolnay@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1480209
Reviewed-by: Andrey Pronin <apronin@chromium.org>

Conflicts:
	drivers/char/tpm/Kconfig
	drivers/char/tpm/Makefile

[rebase54(groeck): Context conflicts; squashed:
	FIXUP: CHROMIUM: Device driver for TPM over virtio
]
Signed-off-by: Guenter Roeck <groeck@chromium.org>
3 files changed