fix(stm32f4-bootloader): disable SysTick interrupt during clock init …

[is-northfish]

Description of the Bug

In the mdk_bootloader.uvprojx routine for the STM32F4 platform, the system encounters a consistent HardFault during startup on custom hardware utilizing a passive crystal oscillator.

Root Cause Analysis:

1. HAL_Init() sets up and enables the SysTick timer and its interrupt.
2. SystemClock_Config() blocks execution while waiting for the HSE oscillator to stabilize (RCC_WaitForHSEOSCReady()).
3. Due to the physical startup delay of passive crystals (unlike the HSE Bypass mode on official evaluation boards, which masks this issue), the SysTick interrupt triggers before the FreeRTOS scheduler has been initialized.
4. The ISR jumps to the FreeRTOS SysTick_Handler and calls xTaskIncrementTick(). Since the scheduler isn't running, it attempts to dereference an uninitialized pxCurrentTCB (NULL pointer), leading to a HardFault.

Proposed Fix

This PR provides a lightweight, register-level fix to resolve the race condition.
By explicitly clearing the SysTick_CTRL_TICKINT_Msk bit immediately after HAL_Init(), the SysTick interrupt is suppressed during the SystemClock_Config() blocking phase.

    /* Reset of all peripherals, Initializes the Systick. */
    HAL_Init();
  
    /* Disable SysTick interrupt to prevent early FreeRTOS tick during HSE delay */
    SysTick->CTRL &= ~SysTick_CTRL_TICKINT_Msk;
    
    /* Configure the system clock to have a system clock = 168 Mhz */
    SystemClock_Config();

[is-northfish]

Status Update:
I have communicated with the DJI PSDK R&D team via official support. They have evaluated and confirmed that this timing race condition indeed exists on custom hardware due to the physical startup delay differences.

The team plans to optimize the Bootloader clock configuration and unify the HAL timebase settings across the RTOS examples in a future release to ensure initialization stability.

I will leave this PR open as a temporary workaround reference for the community until the official fix is rolled out.