Change in coreboot[master]: mainboard/pine64/rockpro64: Add initial Rockpro64 support

[Paul Menzel (Code Review)]

Attention is currently required from: Martin Roth, Moritz Fischer.
Paul Menzel has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/50625 )

Change subject: mainboard/pine64/rockpro64: Add initial Rockpro64 support
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Patch Set 3:

(3 comments)

Commit Message:

https://review.coreboot.org/c/coreboot/+/50625/comment/483f6f03_b7ef56f0 
PS3, Line 9: This adds initial support for the Pine64 Rockpro64 board.
As there is no documentation, please add a little information, what processor it has, how it can be flashed, and how you got the log messages, for example.

https://www.pine64.org/rockpro64/

Patchset:

PS3: 
Welcome to coreboot. It’s awesome seeing you working on this.

File src/mainboard/pine64/rockpro64/board_info.txt:

https://review.coreboot.org/c/coreboot/+/50625/comment/f2e16d8b_21b6fcb7 
PS3, Line 2: RockPro64
Official spelling seems to be ROCKPro64 [1].

[1]: https://www.pine64.org/rockpro64/