FuriHal: do not enable LSECSS if BORRST is active (#1590)

Co-authored-by: あく <alleteam@gmail.com>

firmware/targets/f7/furi_hal/furi_hal_clock.c

@@ -75,7 +75,10 @@ void furi_hal_clock_init() {
         LL_EXTI_LINE_18); /* Why? Because that's why. See RM0434, Table 61. CPU1 vector table. */
     LL_EXTI_EnableRisingTrig_0_31(LL_EXTI_LINE_18);
     LL_RCC_EnableIT_LSECSS();
-    LL_RCC_LSE_EnableCSS();
+    /* ES0394, extended case of 2.2.2 */
+    if(!LL_RCC_IsActiveFlag_BORRST()) {
+        LL_RCC_LSE_EnableCSS();
+    }
 
     /* Main PLL configuration and activation */
     LL_RCC_PLL_ConfigDomain_SYS(LL_RCC_PLLSOURCE_HSE, LL_RCC_PLLM_DIV_2, 8, LL_RCC_PLLR_DIV_2);