fix wrong flashmode report

[Staars]

Description:

ATM Tasmota reports the flash mode of the first boot loader, which might be changed later in the boot process.
This uses the same method as in the bootloader_esp32.cfrom the ESP-IDF and updates the value.
In the future this might be handled differently from Espressif's side by storing this value at boot time in a global struct.

Checklist:

• The pull request is done against the latest development branch
• Only relevant files were touched
• Only one feature/fix was added per PR and the code change compiles without warnings
• The code change is tested and works with Tasmota core ESP8266 V.2.7.4.9
• The code change is tested and works with Tasmota core ESP32 V.2.0.4.1
• I accept the CLA.

NOTE: The code change must pass CI tests. Your PR cannot be merged unless tests pass

[Jason2866]

Tested and verified working, nice!