Add sysutils/u-boot-orangepi-pc2

OrangePi PC2 is an SBC with :

• Allwinner H5 (arm64)
• Three usb ports + one OTG port
• HDMI Connector
• Headphone output
• Microphone
• Ethernet
• ...

Reviewed by: imp
Approved by: imp
Differential Revision: https://reviews.freebsd.org/D13363