[nrf fromtree] samples: drivers: spi_flash: Extend requirements description

The patch updates README with detailed description of  the requirements
regarding target devicetree needed to correctly build the sample.

Signed-off-by: Adam Wojasinski <[email protected]>
(cherry picked from commit 7b78393)

Author: Adam Wojasinski

samples/drivers/spi_flash/README.rst

@@ -14,8 +14,13 @@ savings is correctly implemented.
 Building and Running
 ********************
 
-The application will build only for a target that has a :ref:`devicetree
-<dt-guide>` entry with ``jedec,spi-nor`` as a compatible.
+The application will build only for a target that has a :ref:`devicetree <dt-guide>`
+``spi-flash0`` alias that refers to an entry with one of the following bindings as a compatible:
+
+* :dtcompatible:`jedec,spi-nor`,
+* :dtcompatible:`st,stm32-qspi-nor`,
+* :dtcompatible:`st,stm32-ospi-nor`,
+* :dtcompatible:`nordic,qspi-nor`.
 
 .. zephyr-app-commands::
    :zephyr-app: samples/drivers/spi_flash