slimbus: messaging: remove multiple calls to pm_runtime_mark_last_busy

There seems to be a multiple calls to pm_runtime_mark_last_busy(),
which looks like a typo.
Fix this by properly adding pm_runtime_put_autosuspend to put controller
in auto suspend state.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>