Documentation/platforms/risc-v/eic7700x/boards/starpro64: Add photo of PINE64 StarPro64 SBC

This PR adds a photo of PINE64 StarPro64 SBC to the StarPro64 page.
I shot the photo myself with a Sony NEX-7 camera.

Signed-off-by: Lup Yuen Lee <luppy@appkaki.com>

Author: lupyuen

Documentation/platforms/risc-v/eic7700x/boards/starpro64/index.rst

@@ -6,6 +6,9 @@ PINE64 StarPro64
 is a RISC-V Single-Board Computer based on the ESWIN EIC7700X RISC-V SoC
 with Quad-Core 64-bit RISC-V CPU, 32 GB LPDDR5 RAM and 100 Mbps Ethernet.
 
+.. figure:: starpro64.jpg
+   :align: center
+
 Features
 ========