lib/fs/: Use array notation with forward declarations

Link: n3394 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3394.pdf>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

Author: alejandro-colomar

lib/fs/readlink/readlinknul.c

@@ -9,5 +9,5 @@
 #include <sys/types.h>
 
 
-extern inline ssize_t readlinknul(const char *restrict link, char *restrict buf,
-    ssize_t size);
+extern inline ssize_t readlinknul(ssize_t size;
+    const char *restrict link, char buf[restrict size], ssize_t size);

lib/fs/readlink/readlinknul.h

@@ -21,13 +21,14 @@
 
 
 ATTR_STRING(1)
-inline ssize_t readlinknul(const char *restrict link, char *restrict buf,
-    ssize_t size);
+inline ssize_t readlinknul(ssize_t size;
+    const char *restrict link, char buf[restrict size], ssize_t size);
 
 
 // Similar to readlink(2), but terminate the string.
 inline ssize_t
-readlinknul(const char *restrict link, char *restrict buf, ssize_t size)
+readlinknul(ssize_t size;
+    const char *restrict link, char buf[restrict size], ssize_t size)
 {
 	ssize_t  len;