[media] cx18: fix register range check

Ensure that the register is aligned to a dword, otherwise the range check
could fail since it assumes dword alignment.

Signed-off-by: Hans Verkuil <[e-mail]>
Cc: Andy Walls <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/pci/cx18/cx18-ioctl.c

···
 {
 	struct cx18 *cx = fh2id(fh)->cx;
 
+	if (reg->reg & 0x3)
+		return -EINVAL;
 	if (reg->reg >= CX18_MEM_OFFSET + CX18_MEM_SIZE)
 		return -EINVAL;
 	reg->size = 4;
···
 {
 	struct cx18 *cx = fh2id(fh)->cx;
 
+	if (reg->reg & 0x3)
+		return -EINVAL;
 	if (reg->reg >= CX18_MEM_OFFSET + CX18_MEM_SIZE)
 		return -EINVAL;
 	cx18_write_enc(cx, reg->val, reg->reg);