Several SPI controller drivers have defined differently named properties for
the number of chip selects.  Now adding "num-cs" as a reference name for new
bindings.
Signed-off-by: Roland Stigge <stigge@antcom.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
 chip selects.  Individual drivers can define additional properties to
 support describing the chip select layout.
 
+Optional property:
+- num-cs : total number of chipselects
+
 SPI slave nodes must be children of the SPI master node and can
 contain the following properties.
 - reg             - (required) chip select address of device.