spi: fsl-qspi: Enhance binding to extend example for flash entry

Add example for adding flash entry on various boards' dts
using flash manufacture spansion/cypress.

Signed-off-by: Ashish Kumar <Ashish.Kumar@nxp.com>
Link: https://lore.kernel.org/r/1565691791-26167-3-git-send-email-Ashish.Kumar@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>