valgrind: Add false positive to suppressions file

Valgrind will check that the third argument to ioctl() is a valid
pointer, but some ioctls interpret that argument as an integer, and that
is the case here (it's a file descriptor), so this is a false positive.

https://bugzilla.gnome.org/show_bug.cgi?id=787109

glib.supp

@@ -232,6 +232,16 @@
 	fun:_g_io_module_get_default
 }
 
+# memcheck checks that the third argument to ioctl() is a valid pointer, but
+# some ioctls use that argument as an integer
+{
+   ioctl-with-non-pointer-param
+   Memcheck:Param
+   ioctl(generic)
+   fun:ioctl
+   fun:btrfs_reflink_with_progress
+}
+
 {
 	g-private-get
 	drd:ConflictingAccess