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.

Necessary after this patch replaced open() with lstat():
  http://review.cyanogenmod.org/#/c/31864/

For reference, see JIRAs:
  https://jira.cyanogenmod.org/browse/QSDB-2
  https://jira.cyanogenmod.org/browse/CYAN-536

Change-Id: Ia2cd6386c0e6e649ab8c2ccd47ee845792a8493f