board: esp32: update SPI RAM sample code documentation

size is greater than ESP_HEAP_MIN_EXTRAM_THRESHOLD, memory is allocated from

SPIRAM.

Supported SoCs

**************

The following SoCs are supported by this sample code so far:

* ESP32

* ESP32-S2

Building and Running

********************

Make sure you have the ESP32_WROVER_KIT connected over USB port.

Make sure you have your board connected over USB port.

.. code-block:: console

   west build -b esp32 samples/boards/esp32/spiram_test

   west flash --esp-device /dev/ttyUSB0

   west flash

If using another supported Espressif board, replace the argument in the above

command with a proper board name (e.g., `esp32s2_saola`).

Sample Output

=============

To check output of this sample, any serial console program can be used (i.e. on Linux minicom, putty, screen, etc)

This example uses ``picocom`` on the serial port ``/dev/ttyUS0``:

To check output of this sample, run ``west espressif monitor`` or any other serial

console program (e.g., minicom, putty, screen, etc).

This example uses ``west espressif monitor``, which automatically detects the serial

port at ``/dev/ttyUSB0``:

.. code-block:: console

   $ west espressif monitor

.. code-block:: console