1. Rename m2351_stddriver_sup.h/c to stddriver_secure.h/.c for naming consistency
2. Add hal_secure.h to include hal-exported secure functions
3. Change return/argument type in secure functions:
(1) Change int to int32_t
(2) Change PinName to int32_t
(3) Change time_t to int64_t
4. Update secure lib/bin accordingly
1. Power down RTC access from CPU domain in rtc_free. After rtc_free, RTC gets
inaccessible from CPU domain but keeps counting.
2. Fix RTC cannot cross reset cycle.