tools:iio:generic_buffer: catch errors for arguments conversion

Add handler to catch errors on conversion of numerical arguments.

Signed-off-by: Hartmut Knaack <knaack.h@gmx.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/tools/iio/generic_buffer.c b/tools/iio/generic_buffer.c
index eb89bc2..93ac93f 100644
--- a/tools/iio/generic_buffer.c
+++ b/tools/iio/generic_buffer.c
@@ -206,13 +206,22 @@
 			noevents = 1;
 			break;
 		case 'c':
+			errno = 0;
 			num_loops = strtoul(optarg, &dummy, 10);
+			if (errno)
+				return -errno;
 			break;
 		case 'w':
+			errno = 0;
 			timedelay = strtoul(optarg, &dummy, 10);
+			if (errno)
+				return -errno;
 			break;
 		case 'l':
+			errno = 0;
 			buf_len = strtoul(optarg, &dummy, 10);
+			if (errno)
+				return -errno;
 			break;
 		case 'g':
 			notrigger = 1;