kconfig: add named choice group

As choice dependency are now fully checked, it's quite easy to add support
for named choices. This lifts the restriction that a choice value can only
appear once, although it still has to be within the same group,
but multiple choices can be joined by giving them a name.
While at it I cleaned up a little the choice type logic to simplify it a
bit.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/scripts/kconfig/lkc_proto.h b/scripts/kconfig/lkc_proto.h
index 4d09f6d..8e69461 100644
--- a/scripts/kconfig/lkc_proto.h
+++ b/scripts/kconfig/lkc_proto.h
@@ -21,7 +21,7 @@
 /* symbol.c */
 P(symbol_hash,struct symbol *,[SYMBOL_HASHSIZE]);
 
-P(sym_lookup,struct symbol *,(const char *name, int isconst));
+P(sym_lookup,struct symbol *,(const char *name, int flags));
 P(sym_find,struct symbol *,(const char *name));
 P(sym_re_search,struct symbol **,(const char *pattern));
 P(sym_type_name,const char *,(enum symbol_type type));