msm8660: add dummy open() of /dev/smd0 to avoid in-call audio race condition

This causes smd_tty_open() in arch/arm/mach-msm/smd_tty.c to load
the modem firmware earlier. This is necessary to avoid a race condition
where in-call audio dies if a phone call is made before initialization
has finished.

http://review.cyanogenmod.org/#/c/34019/

Change-Id: I1b8a4ddc465fc88eb7898bae7f8606bfba6a9514