msi-laptop: Detect 3G device exists by standard ec command

Detect 3G device exists by standard ec command. Driver will not create the threeg sysfs
file and threeg rfkill interface if there have no internal 3G device in MSI notebook/netbook.

Signed-off-by: Lee, Chun-Yi <jlee@novell.com>
Cc: Lennart Poettering <mzxreary@0pointer.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>