[bsp][stm32] Add LXB407ZGT6-P1 board support

Add BSP support for the LXB407ZGT6-P1 development board from
Lu Xiao Ban (LXB), based on the STM32F407ZGT6 (Cortex-M4, 168MHz).

- MCU: STM32F407ZGT6, 1MB FLASH, 192KB RAM
- HSE 8MHz / LSE 32.768kHz, SYSCLK 168MHz
- LED: PC13 (active low)
- Console: USART1 (PA9/PA10), 115200-8-1-N

Author: Zepp-Hanzj

bsp/stm32/stm32f407-lxb/.ci/attachconfig/ci.attachconfig.yml

@@ -0,0 +1,12 @@
+devices.soft_i2c:
+  kconfig:
+    - CONFIG_RT_USING_I2C=y
+    - CONFIG_RT_USING_SOFT_I2C=y
+    - CONFIG_RT_USING_SOFT_I2C1=y
+    - CONFIG_RT_SOFT_I2C1_SCL_PIN=24
+    - CONFIG_RT_SOFT_I2C1_SDA_PIN=25
+    - CONFIG_RT_SOFT_I2C1_BUS_NAME="swi2c1"
+    - CONFIG_RT_USING_SOFT_I2C2=y
+    - CONFIG_RT_SOFT_I2C2_SCL_PIN=16
+    - CONFIG_RT_SOFT_I2C2_SDA_PIN=91
+    - CONFIG_RT_SOFT_I2C2_BUS_NAME="swi2c2"