TTY: msm_smd_tty: Remove legacy device init functionality

The legacy device initialization functionality, which was used in cases
where the DT was not used for initialization, is no longer used.

Remove this functionality.

Change-Id: If888c44cff054dc2537c0170a40870006a0632df
Signed-off-by: Steven Cahail <scahail@codeaurora.org>