hw/mcu/stm32f1: Disable SysTick when RTC is selected as tick source

When tick was provided by RTC instead of SysTick (default)
and MCUboot used SysTick during boot, SysTick was never turned off
and was running in application code.
This resulted in two interrupts advancing mynewt OS tick so clock
was running too fast.

Now os_tick_init() from RTC code disables SysTick that could be
started in bootloader

Signed-off-by: Jerzy Kasenberg <[email protected]>

hw/mcu/stm/stm32f1xx/src/rtc_tick_stm32f1xx.c

@@ -120,6 +120,7 @@ os_tick_init(uint32_t os_ticks_per_sec, int prio)
         .PeriphClockSelection = RCC_PERIPHCLK_RTC,
         .RTCClockSelection = RCC_RTCCLKSOURCE_LSE,
     };
+    SysTick->CTRL = 0;
 
     HAL_RCCEx_PeriphCLKConfig(&clock_init);
     __HAL_RCC_RTC_ENABLE();