The CPU might prefetch instructions, which means it in some cases
will try to fetch instruction located after the last instruction in
flash.text.
Add dummy bytes to ensure fetching these wont result in an error,
e.g. MMU exceptions
Goal is that multiple faults would be required to bypass a boot-time signature check.
- Also strengthens some address range checks for safe app memory addresses
- Change pre-enable logic to also check the bootloader signature before enabling SBV2 on ESP32
Add some additional checks for invalid sections:
- Sections only partially in DRAM or IRAM are invalid
- If a section is in D/IRAM, allow the possibility only some is in D/IRAM
- Only pass sections that are entirely in the same type of RTC memory region
