soc/rtc: round APB clock frequency to nearest MHz

components/soc/esp32/rtc_clk.c

@@ -500,7 +500,11 @@ void rtc_clk_apb_freq_update(uint32_t apb_freq)
 
 uint32_t rtc_clk_apb_freq_get()
 {
-    return reg_val_to_clk_val(READ_PERI_REG(RTC_APB_FREQ_REG)) << 12;
+    uint32_t freq_hz = reg_val_to_clk_val(READ_PERI_REG(RTC_APB_FREQ_REG)) << 12;
+    // round to the nearest MHz
+    freq_hz += MHZ / 2;
+    uint32_t remainder = freq_hz % MHZ;
+    return freq_hz - remainder;
 }