kconfig: remove named choice support

Commit 5a1aa8a1 ("kconfig: add named choice group") did not provide
enough explanation regarding its benefits. A use case was found in
another project [1] sometime later, this feature has never been used in
the kernel.

[1]: https://lore.kernel.org/all/201012150034.01356.yann.morin.1998@anciens.enib.fr/Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

Documentation/kbuild/kconfig-language.rst

@@ -393,7 +393,7 @@ of C0, which doesn't depend on M::
 
 choices::
 
-	"choice" [symbol]
+	"choice"
 	<choice options>
 	<choice block>
 	"endchoice"
@@ -412,10 +412,6 @@ the kernel, but all drivers can be compiled as modules.
 
 A choice accepts another option "optional", which allows to set the
 choice to 'n' and no entry needs to be selected.
-If no [symbol] is associated with a choice, then you can not have multiple
-definitions of that choice. If a [symbol] is associated to the choice,
-then you may define the same choice (i.e. with the same entries) in another
-place.
 
 comment::
 

scripts/kconfig/parser.y

@@ -94,7 +94,7 @@ struct menu *current_menu, *current_entry;
 %type <expr> if_expr
 %type <string> end
 %type <menu> if_entry menu_entry choice_entry
-%type <string> word_opt assign_val
+%type <string> assign_val
 %type <flavor> assign_op
 
 %destructor {
@@ -222,13 +222,12 @@ config_option: T_MODULES T_EOL
 
 /* choice entry */
 
-choice: T_CHOICE word_opt T_EOL
+choice: T_CHOICE T_EOL
 {
-	struct symbol *sym = sym_lookup($2, SYMBOL_CHOICE);
+	struct symbol *sym = sym_lookup(NULL, SYMBOL_CHOICE);
 	sym->flags |= SYMBOL_NO_WRITE;
 	menu_add_entry(sym);
 	menu_add_expr(P_CHOICE, NULL, NULL);
-	free($2);
 	printd(DEBUG_PARSE, "%s:%d:choice\n", cur_filename, cur_lineno);
 };
 
@@ -449,9 +448,6 @@ symbol:	  nonconst_symbol
 	| T_WORD_QUOTE	{ $$ = sym_lookup($1, SYMBOL_CONST); free($1); }
 ;
 
-word_opt: /* empty */			{ $$ = NULL; }
-	| T_WORD
-
 /* assignment statement */
 
 assignment_stmt:  T_WORD assign_op assign_val T_EOL	{ variable_add($1, $3, $2); free($1); free($3); }