driver: clock: espressif: always use calibrated frequency

When clock get_rate() is called, return calibrated frequency instead
of nominal one. This improves accuracy specially when internal RC SLOW
clock is used.

Signed-off-by: Sylvio Alves <sylvio.alves@espressif.com>

Author: sylvioalves

drivers/clock_control/clock_control_esp32.c

@@ -567,10 +567,10 @@ static int clock_control_esp32_get_rate(const struct device *dev, clock_control_
 
 	switch ((int)sys) {
 	case ESP32_CLOCK_CONTROL_SUBSYS_RTC_FAST:
-		*rate = esp_clk_tree_lp_fast_get_freq_hz(ESP_CLK_TREE_SRC_FREQ_PRECISION_APPROX);
+		*rate = esp_clk_tree_lp_fast_get_freq_hz(ESP_CLK_TREE_SRC_FREQ_PRECISION_CACHED);
 		break;
 	case ESP32_CLOCK_CONTROL_SUBSYS_RTC_SLOW:
-		*rate = clk_hal_lp_slow_get_freq_hz();
+		*rate = esp_clk_tree_lp_slow_get_freq_hz(ESP_CLK_TREE_SRC_FREQ_PRECISION_CACHED);
 		break;
 	default:
 		*rate = clk_hal_cpu_get_freq_hz();