v4l: xilinx: multi-scaler: Fix warnings for unchecked return value

This patch fixes the coverity warnings about return value not being
checked and improper use of negative value.

The actual warnings are:

For xm2msc_parse_of():
Event check_return: Calling of_property_count_strings without
checking return value
Event unchecked_value: Using value hw_vid_fmt_cnt as a function
argument without checking appropriately

Event negative_return_fn: Function of_property_count_strings
(node, "xlnx,vid-formats") returns a negative number
Event negative_returns: hw_vid_fmt_cnt is passed to a parameter
that cannot be negative

Signed-off-by: Akhil Raghu Menon <akhil.raghu.menon@xilinx.com>
Reviewed-by: Vishal Sagar <vishal.sagar@amd.com>

drivers/media/platform/xilinx/xilinx-multi-scaler.c

@@ -2286,6 +2286,13 @@ static int xm2msc_parse_of(struct platform_device *pdev,
 	/* read supported video formats and update internal table */
 	hw_vid_fmt_cnt = of_property_count_strings(node, "xlnx,vid-formats");
 
+	/* Validate the number of strings returned */
+	if (hw_vid_fmt_cnt < 0)
+		return hw_vid_fmt_cnt;
+
+	if (hw_vid_fmt_cnt > ARRAY_SIZE(formats))
+		return -EINVAL;
+
 	ret = of_property_read_string_array(node, "xlnx,vid-formats",
 					    vid_fmts, hw_vid_fmt_cnt);
 	if (ret < 0) {