lib/string_helpers: Change returned value of the strreplace()

It's more useful to return the pointer to the string itself
with strreplace(), so it may be used like

attr->name = strreplace(name, '/', '_');

While at it, amend the kernel documentation.

Signed-off-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Kees Cook <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

include/linux/string.h

···
 #endif
 
 void *memchr_inv(const void *s, int c, size_t n);
-char *strreplace(char *s, char old, char new);
+char *strreplace(char *str, char old, char new);
 
 extern void kfree_const(const void *x);
 

lib/string_helpers.c

···
 
 /**
  * strreplace - Replace all occurrences of character in string.
- * @s: The string to operate on.
+ * @str: The string to operate on.
  * @old: The character being replaced.
  * @new: The character @old is replaced with.
  *
- * Returns pointer to the nul byte at the end of @s.
+ * Replaces the each @old character with a @new one in the given string @str.
+ *
+ * Return: pointer to the string @str itself.
  */
-char *strreplace(char *s, char old, char new)
+char *strreplace(char *str, char old, char new)
 {
+	char *s = str;
+
 	for (; *s; ++s)
 		if (*s == old)
 			*s = new;
-	return s;
+	return str;
 }
 EXPORT_SYMBOL(strreplace);