[libc][syscall]移除libc_stdio_read/write函数，优化syscall

components/libc/compilers/dlib/stdio.c

@@ -46,13 +46,4 @@ int libc_stdio_get_console(void) {
     return std_fd;
 }
 
-int libc_stdio_read(void *buffer, size_t size)
-{
-    return read(std_fd, buffer, size);
-}
-
-int libc_stdio_write(const void *buffer, size_t size)
-{
-    return write(std_fd, buffer, size);
-}
 #endif