* Fix config key search which could cause camera_autodetect to fail
The bootvar0 config property was added in the wrong section which
could cause the config property search for some other properties
to fail.
* arm_loader: Also require the early-watchdog property
The change correcting the implementation of dtoverlay_is_enabled had the
unintended consequence of causing the firmware to enable the watchdog
even though the user had not explicitly requested it. This is harmless
on Linux because the watchdog driver takes over and disarms it, but on
other operating systems this can lead to a reboot. Avoid this problem
by also requiring the presence of a new property, "early-watchdog".
See: https://github.com/raspberrypi/firmware/issues/1980
* helpers/config_loader: Add bootvar0 eeprom config that can be used in config.txt section expressions
This allows an eeprom config setting (e.g. BOOTARG0=0x10) to be set on a board
which config.txt can use as a conditional expression (e.g. [bootarg0&0x10]).
* arm_loader: Fix boot-watchdog stop on Pi4
Fix a problem where the boot_watchdog heartbeat timer was not
stopped correctly which could cause it to clash with the kernel
watchdog driver.
