Xmc flash 2

[ChocolateFrogsNuts]

Remove the unnecessary XMC chip support from eboot and verify the flash contents after copying new firmware.

Testing shows there should be no issue with the XMC chips in eboot because the flash access speed is always 20MHz, however verifying the content written will help identify any issues if they do occur.
The additional code is minimal, and as it only reads, the verify is very quick.

[Tech-TX]

That works with both failing cases for me (OTA upload and ESP.restart() at 160MHz),
#7307
#7267

I've already merged #7277 into my local fork, so I'm not sure if #7267 is needed in addition to this PR.

[devyte]

@Tech-TX #7277 was a rollback of the first implementation. This should be the fixed final solution.

[devyte]

Code wise it looks good.

[earlephilhower]

LGTM. I'm not sure what the point of checking is. The way the code is written, you'll get an error, print a failure code, clear the command buffer and then SWRESET. At that time it'll just LOAD_APP anyway, same as if it passed verification.

That said, I can't give a much better idea of what to do in that case, anyway. Don't want to continually overwrite (i.e. don't clear the cmd so next reboot will try writing again) as you could end up in a hard reboot-write-reboot-write...loop and destroy the flash.

[devyte]

The verify is supposed to cover the case when the flash write seems to succeed, i. e. no error, but in truth it didn't take at hw level due to whatever reason.

[ChocolateFrogsNuts]

@earlephilhower the check is relatively cheap (in terms of code size and execution time) and if we do have problems with OTA updates to XMC chips will make it easy to identify if it is a problem with writing to the chip.
Theoretically we could store ACTION_COPY_FAILED in the RTC and have that cause printing the error and a while(true){}
That way if an OTA update copy failed, the chip would halt, then you could connect to the USB and press reset to get the reason dumped to monitor. If the eboot command is moved to a non-volatile location, it would even work over power cycles (although you would need to clear that the eboot command as part of a USB update).