Switch fwu_boottime_checks() from EVT_MAIN_LOOP to EVT_POST_PREBOOT
because there is no reason to call FWU so early. FWU triggers EFI
stack initialization before all devices are visible which prevents
the EFI stack from scanning these devices and adding them to EFI
variables.
Signed-off-by: Michal Simek <michal.simek@amd.com>
Reviewed-by: Simon Glass <sjg@chromium.org>