ARM: dts: s5pv210: align SPI GPIO node name with dtschema in Aries

The device tree schema expects SPI controller to be named "spi",
otherwise dtbs_check complain with a warning like:

  spi-gpio-0: $nodename:0: 'spi-gpio-0' does not match '^spi(@.*|-[0-9a-f])*$'

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Tested-by: Jonathan Bakker <xc-racer2@live.ca>
Link: https://lore.kernel.org/r/20200907161141.31034-25-krzk@kernel.org