serial: msm_serial_hs: Optimize the total tty port support

No need of having high number of tty port for HSUART which just wastes
resources. Make this optimal based on the use cases.

Change-Id: If82fc1a3457fae7503d7557817ca776f19027da7
Signed-off-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>