Staging: htc: Dream: limit Kconfig for only MSM platforms

Limit SMD communication glue to MSM platform. It is closely tied to
MSM architecture.

Signed-off-by: Pavel Machek <pavel@ucw.cz>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>