ARM: dts: bcm4709: fix bus range assignment

The netgear r8000 dts file limits the bus range for the first host
bridge to exclude bus 0, but the two devices on the first bus are
explicitly assigned to bus 0, causing a build time warning:

/home/arnd/arm-soc/arch/arm/boot/dts/broadcom/bcm4709-netgear-r8000.dts:142.3-27: Warning (pci_device_bus_num): /axi@18000000/pcie@13000/pcie@0/pcie@0,0/pcie@1,0:bus-range: PCI bus number 0 out of range, expected (1 - 255)
/home/arnd/arm-soc/arch/arm/boot/dts/broadcom/bcm4709-netgear-r8000.dts:142.3-27: Warning (pci_device_bus_num): /axi@18000000/pcie@13000/pcie@0/pcie@0,0/pcie@2,0:bus-range: PCI bus number 0 out of range, expected (1 - 255)

As Rosen mentioned, the bus-range property was a mistake, so just
remove it and keep the reg values pointing to bus 0, which is
allowed by the default bus range of the SoC.

Fixes: 893faf67438c ("ARM: dts: BCM5301X: add root pcie bridges")
Suggested-by: Rosen Penev <rosenp@gmail.com>
Link: https://lore.kernel.org/r/20260414064754.3129667-1-arnd@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>