tpm: Add 'tpm autostart' shell command

tpm: Add 'tpm autostart' shell command

For a TPM device to be operational we need to initialize it and
perform its startup sequence.  The 'tpm init' command currently calls
tpm_init() which ends up calling the ->open() per-device callback and
performs the initial hardware configuration as well as requesting
locality 0 for the caller.  There no code that currently calls
tpm_init() without following up with a tpm_startup() and tpm_self_test_full()
or tpm_continue_self_test().

So let's add a 'tpm autostart' command and call tpm_auto_start() which
leaves the device in an operational state.

It's worth noting that calling tpm_init() only, doesn't allow a someone
to use the TPM since the startup sequence is mandatory. We always
repeat the pattern of calling
- tpm_init()
- tpm_startup()
- tpm_self_test_full() or tpm_continue_self_test()

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>