iio: adc: xilinx: Remove dead code from xadc_zynq_setup

This patch removes dead code from xadc_zynq_setup. The condition
"if (tck_rate > XADC_ZYNQ_TCK_RATE_MAX)" cannot be true at any point of
time. There is also an incompatible parameter used in the code.
This patch fixes the same reported by coverity.
Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/xilinx-xadc-core.c

@@ -341,8 +341,6 @@ static int xadc_zynq_setup(struct platform_device *pdev,
 
 	pcap_rate = clk_get_rate(xadc->clk);
 
-	if (tck_rate > XADC_ZYNQ_TCK_RATE_MAX)
-		tck_rate = XADC_ZYNQ_TCK_RATE_MAX;
 	if (tck_rate > pcap_rate / 2) {
 		div = 2;
 	} else {
@@ -1045,7 +1043,7 @@ static int xadc_parse_dt(struct iio_dev *indio_dev, struct device_node *np,
 	unsigned int num_channels;
 	const char *external_mux;
 	u32 ext_mux_chan;
-	int reg;
+	u32 reg;
 	int ret;
 
 	*conf = 0;