spi: dt-bindings: spi-controller: Fix #address-cells for slave mode

spi: dt-bindings: spi-controller: Fix #address-cells for slave mode

Currently, the DT bindings for an SPI controller specify that
"#address-cells" must be fixed to one.  However, that applies to an SPI
controller in master mode only.  When running in SPI slave mode,
"#address-cells" should not be specified.

Fix this making "#address-cells" mutually-exclusive with "spi-slave".

Fixes: 0a1b929356830257 ("spi: Add YAML schemas for the generic SPI options")
Reported-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200306085038.8111-2-geert+renesas@glider.be
Signed-off-by: Mark Brown <broonie@kernel.org>