fix: Allow the espefuse.py to work when coding scheme == 3 (ESPTOOL-803)

[klondi]

When the coding scheme efuse has the value 3, the efuse fields should still be considered to be 256 bits long. Unfortunately, the tool fails miserably with error "A fatal error occurred: Coding scheme (3) not supported"

This patch addresses that by handling the case when coding scheme is 0 in the same way as if coding scheme was 1.

This change fixes the following bug(s):

I have tested this change with the following hardware & software combinations:

ESP32 with coding scheme == 3

I have run the esptool.py automated integration tests with this change and the above hardware:

NO TESTING

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[KonstantinKondrashov]

Hi @klondi!
Thanks for your contribution. Yes, I confirm that for the coding scheme = 3 there is no support for now. I will check other places where it can affect, it can be easily added. It relates to the ESP32 chip only.

[KonstantinKondrashov]

I will make support for coding scheme == 3 for espefuse.py but I want to mention that IDF does not support this mode.
If you got the original chip with the coding scheme == 0b01 ("3/4") and then burned another bit to get the "None" coding scheme (val==0b11) then if there were data written in BLOCK1-3 you will see that data in these BLCOKs are mixed with the coding data. It is not recommended way. Why did not do that?

esptool.py recognizes this state as - Coding Scheme Invalid.

This support will allow you to burn data with espefuse.py. However, using this chip with IDF can be limited.
Thanks.

[radimkarnis]

@klondi thank you for the contribution!