uncrustify: split lines at 80 chars

uncrustify-riot.cfg

@@ -10,6 +10,12 @@ indent_label            = 1                 # pos: absolute col, neg: relative c
 indent_switch_case      = 4                 # number
 indent_ternary_operator = 2                 # When the `:` is a continuation, indent it under `?`
 
+#
+# line splitting
+#
+
+code_width              = 80      # Try to limit code width to N columns.
+
 #
 # inter-symbol newlines
 #