scripts/kallsyms: replace prefix_underscores_count() with strspn()

You can do equivalent things with strspn(). I do not see noticeable
performance difference.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kallsyms.c

@@ -661,16 +661,6 @@ static int may_be_linker_script_provide_symbol(const struct sym_entry *se)
 	return 0;
 }
 
-static int prefix_underscores_count(const char *str)
-{
-	const char *tail = str;
-
-	while (*tail == '_')
-		tail++;
-
-	return tail - str;
-}
-
 static int compare_symbols(const void *a, const void *b)
 {
 	const struct sym_entry *sa;
@@ -699,8 +689,8 @@ static int compare_symbols(const void *a, const void *b)
 		return wa - wb;
 
 	/* sort by the number of prefix underscores */
-	wa = prefix_underscores_count(sym_name(sa));
-	wb = prefix_underscores_count(sym_name(sb));
+	wa = strspn(sym_name(sa), "_");
+	wb = strspn(sym_name(sb), "_");
 	if (wa != wb)
 		return wa - wb;