tty: Add msm_smd_tty driver

msm_smd_tty driver provides tty device interface
to 'DS' and 'GPSNMEA' streaming SMD ports.

Cc: Brian Swetland <swetland@google.com>
Signed-off-by: Niranjana Vishwanathapura <nvishwan@codeaurora.org>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>