linker_lists: fix comment

The section name and the C variable name seem to be opposite.
Signed-off-by: NMasahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Marek Vasut <marex@denx.de>
Acked-by: NMarek Vasut <marex@denx.de>

include/linker_lists.h

@@ -28,11 +28,11 @@
  * together. Assuming _list and _entry are the list and entry names,
  * then the corresponding input section name is
  *
- *   _u_boot_list + _2_ + @_list + _2_ + @_entry
+ *   .u_boot_list_ + 2_ + @_list + _2_ + @_entry
  *
  * and the C variable name is
  *
- *   .u_boot_list_ + 2_ + @_list + _2_ + @_entry
+ *   _u_boot_list + _2_ + @_list + _2_ + @_entry
  *
  * This ensures uniqueness for both input section and C variable name.
  *