[media] cx24116: fix a buffer overflow when checking userspace params

The maximum size for a DiSEqC command is 6, according to the
userspace API. However, the code allows to write up much more values:
	drivers/media/dvb-frontends/cx24116.c:983 cx24116_send_diseqc_msg() error: buffer overflow 'd->msg' 6 <= 23

Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
static int cx24116_set_inversion(struct cx24116_state *state,
	fe_spectral_inversion_t inversion)
{
	dprintk("%s(%d)\n", __func__, inversion);

	switch (inversion) {
	case INVERSION_OFF:
		state->dnxt.inversion_val = 0x00;
		break;
	case INVERSION_ON:
		state->dnxt.inversion_val = 0x04;
		break;
	case INVERSION_AUTO:
		state->dnxt.inversion_val = 0x0C;
		break;
	default:
		return -EINVAL;
	}

	state->dnxt.inversion = inversion;

	return 0;
}

static int cx24116_set_inversion(struct cx24116_state *state,
	fe_spectral_inversion_t inversion)
{
	dprintk("%s(%d)\n", __func__, inversion);

	switch (inversion) {
	case INVERSION_OFF:
		state->dnxt.inversion_val = 0x00;
		break;
	case INVERSION_ON:
		state->dnxt.inversion_val = 0x04;
		break;
	case INVERSION_AUTO:
		state->dnxt.inversion_val = 0x0C;
		break;
	default:
		return -EINVAL;
	}

	state->dnxt.inversion = inversion;

	return 0;
}
