samples: display: lvgl: add note about LOG_STRDUP settings

Add a note to warn users about the need to adjust
CONFIG_LOG_STRDUP_BUF_COUNT and/or CONFIG_LOG_STRDUP_MAX_STRING when
deferred logging is enabled.

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>

samples/display/lvgl/README.rst

@@ -39,6 +39,12 @@ or
 Building and Running
 ********************
 
+.. note::
+   When deferred logging is enabled you will likely need to increase
+   :option:`CONFIG_LOG_STRDUP_BUF_COUNT` and/or
+   :option:`CONFIG_LOG_STRDUP_MAX_STRING` to make sure no messages are lost or
+   truncated.
+
 Example building for :ref:`nrf52840dk_nrf52840`:
 
 .. zephyr-app-commands::