tty: n_smux: Rename SSR unit tests

Running the Subsystem Restart (SSR) unit tests without SSR enabled
causes the system to halt.

Rename SSR unit tests to allow for testing all non-SSR tests
quickly from the command line.

Change-Id: Ib80e9adef8311ebe038f878dfcf2aecd1087a471
Signed-off-by: Eric Holmberg <eholmber@codeaurora.org>