arm64: dts: cavium: fix PCI bus dtc warnings

dtc recently added PCI bus checks. Fix these warnings:

arch/arm64/boot/dts/cavium/thunder2-99xx.dtb: Warning (pci_bridge): Node /pci missing bus-range for PCI bridge
arch/arm64/boot/dts/cavium/thunder2-99xx.dtb: Warning (unit_address_vs_reg): Node /pci has a reg or ranges property, but no unit name

Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Jayachandran C <jnair@caviumnetworks.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>