arm64: dts: rockchip: remove duplicate SPI aliases for helios64

An earlier commit defined an alias for all SPI controllers found on the
RK3399, so there's no need to duplicate the aliases in helios64's device
tree.

Cc: Quentin Schulz <foss+kernel@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Link: https://lore.kernel.org/r/20240109-rk3399-spi-aliases-v1-2-2009e44e734a@theobroma-systems.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>