kconfig: Clarify menu and 'if' dependency propagation

It is not obvious that the last two cases refer to menus and ifs,
respectively, in the conditional that sets 'parentdep'.

Automatic submenu creation is done later, so the parent can't be a
symbol here.

No functional changes. Only comments added.
Signed-off-by: NUlf Magnusson <ulfalizer@gmail.com>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/menu.c

@@ -332,8 +332,10 @@ void menu_finalize(struct menu *parent)
 			 */
 			parentdep = expr_alloc_symbol(sym);
 		} else if (parent->prompt)
+			/* Menu node for 'menu' */
 			parentdep = parent->prompt->visible.expr;
 		else
+			/* Menu node for 'if' */
 			parentdep = parent->dep;
 
 		/* For each child menu node... */