Add pure sofware keymaster context

The legacy software keymaster context has support
for wrapping legacy keymaster devices. The keymaster
context added with this patch is a pure openssl based
implementation of a keymaster context.

Test: This code cannot be reached by the VTS test.
      It will be reachable with the next patch which
      adds a Keymaster3 implementation based on this
      software keymaster context.

Bug: 67358942
Change-Id: If9d07f8f7027fa54e41f7367a85f48c56d88c33c
3 files changed