kconfig: stop supporting '.' and '/' in unquoted words

In my understanding, special characters such as '.' and '/' are
supported in unquoted words to use bare file paths in the "source"
statement.

With the previous commit surrounding all file paths with double
quotes, we can drop this.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/preprocess.c

@@ -555,8 +555,7 @@ char *expand_string(const char *in)
 
 static bool is_end_of_token(char c)
 {
-	/* Why are '.' and '/' valid characters for symbols? */
-	return !(isalnum(c) || c == '_' || c == '-' || c == '.' || c == '/');
+	return !(isalnum(c) || c == '_' || c == '-');
 }
 
 /*

scripts/kconfig/zconf.l

@@ -160,7 +160,7 @@ n	[A-Za-z0-9_-]
 		BEGIN(STRING);
 	}
 	\n	BEGIN(INITIAL); return T_EOL;
-	({n}|[/.])+	{
+	{n}+	{
 		const struct kconf_id *id = kconf_id_lookup(yytext, yyleng);
 		if (id && id->flags & TF_PARAM) {
 			yylval.id = id;
@@ -170,7 +170,7 @@ n	[A-Za-z0-9_-]
 		yylval.string = text;
 		return T_WORD;
 	}
-	({n}|[/.$])+	{
+	({n}|$)+	{
 		/* this token includes at least one '$' */
 		yylval.string = expand_token(yytext, yyleng);
 		if (strlen(yylval.string))