esp32/README: Add --init to submodule update command.
Add --init to the submodule update example, thus, all submodules get
initialised including the nested (--recursive) ones.  Without it there
might not be a submodule init.
@@ -32,7 +32,7 @@ git hash of this version can be found by running `make` without a configured
$ git clone https://github.com/espressif/esp-idf.git
$ git checkout <Current supported ESP-IDF commit hash>
- $ git submodule update --recursive
+ $ git submodule update --init --recursive
The binary toolchain (binutils, gcc, etc.) can be installed using the following
guides:
