V4L/DVB (8287): sms1xxx: fix WARNING: unnecessary cast may hide bugs

fix the following checkpatch.pl warning:

WARNING: unnecessary cast may hide bugs,
see http://c-faq.com/malloc/mallocnocast.html



596: FILE: linux/drivers/media/dvb/siano/smscoreapi.c:540:
+	msg = (struct SmsMsgHdr_ST *) kmalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>