ARM: dts: rockchip: Fix erroneous SPI bus dtc warnings on rk3036

dtc has new checks for SPI buses. The rk3036 dts file has a node named
spi' which causes false positive warnings. As the node is a pinctrl child
node, change the node name to be 'spi-pins' to fix the warnings.

arch/arm/boot/dts/rk3036-evb.dtb: Warning (spi_bus_bridge): /pinctrl/spi: incorrect #address-cells for SPI bus
arch/arm/boot/dts/rk3036-kylin.dtb: Warning (spi_bus_bridge): /pinctrl/spi: incorrect #address-cells for SPI bus
arch/arm/boot/dts/rk3036-evb.dtb: Warning (spi_bus_bridge): /pinctrl/spi: incorrect #size-cells for SPI bus
arch/arm/boot/dts/rk3036-kylin.dtb: Warning (spi_bus_bridge): /pinctrl/spi: incorrect #size-cells for SPI bus

Cc: Heiko Stuebner <heiko@sntech.de>
Cc: linux-rockchip@lists.infradead.org
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>