dt-bindings: riscv: starfive: add Star64 board compatible

Add pine64,star64 to JH7110 compatibility. The Pine64 Star64 is a
development board based on the Starfive JH7110 SoC. The board features:

- JH7110 SoC
- 4/8 GiB LPDDR4 DRAM
- AXP15060 PMIC
- 40 pin GPIO header
- 1x USB 3.0 host port
- 3x USB 2.0 host port
- 1x eMMC slot
- 1x MicroSD slot
- 1x QSPI Flash
- 2x 1Gbps Ethernet port
- 1x HDMI port
- 1x 4-lane DSI
- 1x 2-lane CSI
- 1x PCIe 2.0 x1 lane

Signed-off-by: Henry Bell <dmoo_dv@protonmail.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>