arm64: dts: rockchip: Add vcc-supply to SPI flash on Pinephone Pro

arm64: dts: rockchip: Add vcc-supply to SPI flash on Pinephone Pro

As documented in the PinephonePro-Schematic-V1.0-20211127.pdf,
page 11, the SPI Flash's VCC pin is connected to VCC_1V8 power
source. This fixes the following warning:

  spi-nor spi1.0: supply vcc not found, using dummy regulator

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Ondřej Jirman <megi@xff.cz>
Link: https://lore.kernel.org/r/20250827143501.1646163-1-pbrobinson@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>