tpm_manager: Add TpmNvram interface

This CL adds the TpmNvram class interface. This class will
be used to perform operations on TPM NVRAM, and to expose
TPM backed NVRAM to clients of TpmManager via DBus.

Bug: 24059574
TEST=None

Change-Id: I367fd746785fc50ba83a34d51e4be96bb700c553
4 files changed