Use low power RTC on mimxrt10xx (Teensy41) boards

There are apparently two RTC interfaces in the mimxrt10xx dev
kit. The low power interface access the battery backed up hardware.

I've tested this on the Teensy41 and it seems to
fix issue #4574

Author: RetiredWizard

ports/mimxrt10xx/Makefile

@@ -109,6 +109,7 @@ SRC_SDK := \
 	drivers/fsl_ocotp.c \
 	drivers/fsl_pwm.c \
 	drivers/fsl_snvs_hp.c \
+	drivers/fsl_snvs_lp.c \
 	drivers/fsl_tempmon.c \
 	drivers/fsl_trng.c \
 	system_$(CHIP_FAMILY).c \

ports/mimxrt10xx/common-hal/rtc/RTC.c

@@ -36,18 +36,26 @@
 #include "supervisor/shared/translate/translate.h"
 
 #include "fsl_snvs_hp.h"
+#include "fsl_snvs_lp.h"
 
 void rtc_init(void) {
-    snvs_hp_rtc_config_t config;
-    SNVS_HP_RTC_GetDefaultConfig(&config);
+    snvs_hp_rtc_config_t hpconfig;
+    SNVS_HP_RTC_GetDefaultConfig(&hpconfig);
 
-    SNVS_HP_RTC_Init(SNVS, &config);
+    SNVS_HP_RTC_Init(SNVS, &hpconfig);
+
+    snvs_lp_srtc_config_t lpconfig;
+    SNVS_LP_SRTC_GetDefaultConfig(&lpconfig);
+
+    SNVS_LP_SRTC_Init(SNVS, &lpconfig);
+
+    SNVS_LP_SRTC_StartTimer(SNVS);
     SNVS_HP_RTC_StartTimer(SNVS);
 }
 
 void common_hal_rtc_get_time(timeutils_struct_time_t *tm) {
-    snvs_hp_rtc_datetime_t rtcDate;
-    SNVS_HP_RTC_GetDatetime(SNVS, &rtcDate);
+    snvs_lp_srtc_datetime_t rtcDate;
+    SNVS_LP_SRTC_GetDatetime(SNVS, &rtcDate);
 
     tm->tm_year = rtcDate.year;
     tm->tm_mon = rtcDate.month;
@@ -58,15 +66,15 @@ void common_hal_rtc_get_time(timeutils_struct_time_t *tm) {
 }
 
 void common_hal_rtc_set_time(timeutils_struct_time_t *tm) {
-    snvs_hp_rtc_datetime_t rtcDate;
+    snvs_lp_srtc_datetime_t rtcDate;
     rtcDate.year = tm->tm_year;
     rtcDate.month = tm->tm_mon;
     rtcDate.day = tm->tm_mday;
     rtcDate.hour = tm->tm_hour;
     rtcDate.minute = tm->tm_min;
     rtcDate.second = tm->tm_sec;
 
-    SNVS_HP_RTC_SetDatetime(SNVS, &rtcDate);
+    SNVS_LP_SRTC_SetDatetime(SNVS, &rtcDate);
 }
 
 int common_hal_rtc_get_calibration(void) {