Fix flash/monitoring of 26mhz targets

[SergioGasquez]

• Remove InvalidSerialRead error
• Fix Clippy lints
• Update monitoring baudrate when using stub
• Update ESP32-C2 stub to support 26MHz targets. Stubs have been generated using esp-flasher-stub, which uses esp-hal with the changes of this branch: esp-rs/esp-hal@main...SergioGasquez:esp-hal:feat/clk-src

Thanks @bjoernQ for the help resolving this issue

I've reverted the changes for ESP32, as I dont have a 26MHz to test it, I dont know if anyone from the team has one, and ESP32 cant choose xtal_clock as UART source. From ESP32 TRM:

The UART block can derive its clock from two
sources: the 80-MHz APB_CLK, or the reference clock REF_TICK (please refer to Chapter Reset and Clock for
more details). These two clock sources can be selected by configuring UART_TICK_REF_ALWAYS_ON.

UART_TICK_REF_ALWAYS_ON This register is used to select the clock; 1: APB clock; 0: REF_TICK

Tests

• I've build and flash the rng example of esp-hal to a 26MHz C2 and a 40MHz C2 with no issues
  • Monitoring also worked fine
• Board info shows the proper freq for both 26 and 40 MHz

[bjoernQ]

LGTM - works fine for me with both 26 and 40 MHz ESP32-C2