COMPMID-582: Add validation to channel_extract kernels.

Change-Id: I5022d02f06f9d849dad76e3d9b8e48632c236429
Reviewed-on: https://eu-gerrit-1.euhpc.arm.com/121191
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>
Tested-by: Jenkins <bsgcomp@arm.com>
diff --git a/utils/TypePrinter.h b/utils/TypePrinter.h
index e1a5617..63fba35 100644
--- a/utils/TypePrinter.h
+++ b/utils/TypePrinter.h
@@ -523,6 +523,13 @@
     return os;
 }
 
+inline std::string to_string(const Channel &channel)
+{
+    std::stringstream str;
+    str << channel;
+    return str.str();
+}
+
 /** Formatted output of the BorderMode type. */
 inline ::std::ostream &operator<<(::std::ostream &os, const BorderMode &mode)
 {