rtc: Fix minor const char* correction issue
#define RTC_CNTL_MEM_FORCE_NOISO (RTC_CNTL_SLOWMEM_FORCE_NOISO | RTC_CNTL_FASTMEM_FORCE_NOISO)
-static char *TAG = "rtcinit";
+static const char *TAG = "rtcinit";
void rtc_init(rtc_config_t cfg)
{
