Fix SKR/GTR PeripheralPins.c (#17937)

* Add a separate GTR board/variant.
* Revert SKR Pro MOSI (before 248b7dfa59).

buildroot/share/PlatformIO/boards/BigTree_GTR_v1.json

@@ -0,0 +1,46 @@
+{
+  "build": {
+    "core": "stm32",
+    "cpu": "cortex-m4",
+    "extra_flags": "-DSTM32F4 -DSTM32F407xx -DSTM32F40_41xxx",
+    "f_cpu": "168000000L",
+    "hwids": [
+      [
+        "0x1EAF",
+        "0x0003"
+      ],
+      [
+        "0x0483",
+        "0x3748"
+      ]
+    ],
+    "mcu": "stm32f407zgt6",
+    "variant": "BIGTREE_GTR_V1"
+  },
+  "debug": {
+    "jlink_device": "STM32F407ZG",
+    "openocd_target": "stm32f4x",
+    "svd_path": "STM32F40x.svd"
+  },
+  "frameworks": [
+    "arduino"
+  ],
+  "name": "STM32F407ZG (192k RAM. 1024k Flash)",
+  "upload": {
+    "disable_flushing": false,
+    "maximum_ram_size": 196608,
+    "maximum_size": 1048576,
+    "protocol": "stlink",
+    "protocols": [
+      "stlink",
+      "dfu",
+      "jlink"
+    ],
+    "offset_address": "0x8008000",
+    "require_upload_port": true,
+    "use_1200bps_touch": false,
+    "wait_for_upload_port": false
+  },
+  "url": "http://www.st.com/en/microcontrollers/stm32f407zg.html",
+  "vendor": "Generic"
+}