spi: Use 'flash' node name instead of 'spi-flash' in example

Change the nodename in the example with spi-nand from 'spi-flash@1'
to 'flash@1' to make the schema uniform with both spi-nand and spi-nor
flashes. jedec,spi-nor.yaml uses 'flash@' nodename for spi-nor flashes,
so make the spi-nand examples in dt-bindings use it too for uniformity.

Signed-off-by: Apurva Nandan <a-nandan@ti.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210920142713.129295-3-a-nandan@ti.com


Signed-off-by: Mark Brown <broonie@kernel.org>