mctp: add memory_mappings to i2c_server process

Add i2c_regs and scu device mappings to the i2c_server process in the
AST1060-EVB MCTP system configuration, matching what is already present
in the i2c-slave system config.

Without these mappings the kernel will not grant the i2c_server process
access to the I2C peripheral block (0x7e7b0000) or the SCU register
block (0x7e6e2000). The latter is required by ClockConfig::from_hardware()
which reads SCU310 at boot to derive the APB clock frequency used for
I2C timing calculations.

target/ast1060-evb/mctp/system.json5

diff --git a/target/ast1060-evb/mctp/system.json5 b/target/ast1060-evb/mctp/system.json5
index 510bf1a..86c2abd 100644
--- a/target/ast1060-evb/mctp/system.json5
+++ b/target/ast1060-evb/mctp/system.json5
@@ -49,7 +49,25 @@
                         name: "i2c server thread",
                         stack_size_bytes: 4096,   // 4KB stack
                     },
-                ],
+                ],                
+                memory_mappings: [
+                    {
+                        // AST1060 I2C peripheral block: I2cglobal through I2cFilter
+                        // Base: 0x7e7b0000, covers all 14 controllers + buffers + filter
+                        name: "i2c_regs",
+                        type: "device",
+                        start_address: 0x7e7b0000,
+                        size_bytes: 0x4000,
+                    },
+                    {
+                        // SCU register block — scu310 at +0x310 is read by
+                        // ClockConfig::from_hardware() to derive APB clock frequency.
+                        name: "scu",
+                        type: "device",
+                        start_address: 0x7e6e2000,
+                        size_bytes: 0x1000,
+                    },
+                ],            
             },
         },
         // ──── MCTP Server ────