tools/nolibc: remove __nolibc_enosys() fallback from dup2()

All architectures have one of the real functions available.
The additional fallback to __nolibc_enosys() is superfluous.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250821-nolibc-enosys-v1-3-4b63f2caaa89@weissschuh.net

tools/include/nolibc/sys.h

@@ -248,10 +248,8 @@ int sys_dup2(int old, int new)
 	}
 
 	return my_syscall3(__NR_dup3, old, new, 0);
-#elif defined(__NR_dup2)
-	return my_syscall2(__NR_dup2, old, new);
 #else
-	return __nolibc_enosys(__func__, old, new);
+	return my_syscall2(__NR_dup2, old, new);
 #endif
 }