Add Hasivo S1100P-8GT-1SX-S hardware profile (#585)

* Add Hasivo board definition and documentation Hasivo S1100P

doc/devices/Hasivo-S1100P-8GT-1SX-S.md

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+# Hasivo S1100P-8GT-1SX-S
+
+RTL8373N switch with 8 × 2.5G RJ45 ports and 1 × SFP port. GD25Q16 2 MiB flash.
+
+## Port mapping
+
+| Front port | ASIC MAC | Interface |
+| --- | --- | --- |
+| 1–8 | 0–7 | RJ45 |
+| 9 | 8 | SFP (SDS1) |
+
+## Board signals
+
+| Function | GPIO |
+| --- | --- |
+| SFP detect | 38 |
+| SFP LOS | 37 |
+| SFP TX disable | Not connected (`GPIO_NA`) |
+| SFP I2C SDA / SCL | 39 / 40 |
+| Reset | 54 |
+
+PoE is managed by an RTL8238B and a separate STC8H8K64U controller, not directly by the RTL8373N. RTLPlayground does not control PoE on this board.
+
+## Build
+
+`make MACHINE=HASIVO_S1100P_8GT_1SX_S CI=1`
+
+## Photos
+
+Front panel:
+
+![Front panel](photos/Hasivo-S1100P-8GT-1SX-S/front.jpg)
+
+PCB top:
+
+![PCB top](photos/Hasivo-S1100P-8GT-1SX-S/pcb_top.jpg)
+
+PCB bottom:
+
+![PCB bottom](photos/Hasivo-S1100P-8GT-1SX-S/pcb_bottom.jpg)
+