arch/avr/src/avrdx: Add TWI support, fix missing pins code, doc update.

[cederom]

Summary

This is a PR transfer from kerogit delivered over mailing list.

1. This patch adds support for Two-Wire interface in AVR Dx chips. Only master mode is supported in this version.

2. The Kconfig configuration was offering alternate routing options for USART peripherals but there was no code which would act on those settings. This patch fixes it.

3. Additionally, since the code is being worked on, this patch also renames USART-related configuration options from AVR_HAS_ to AVR_HAVE_. This is based on GitHub and mailing list discussion where it was pointed out that other architectures use "HAVE".

4. Documentation updates and fixes.

Depends-on: #17403.

Impact

• AVR Dx: Adds support for TWI on AVR Dx chips.
• AVR Dx: Adds missing code for USART alternate routing.
• AVR Dx: Documentation update.

Testing

1. The driver was tested using TC74Ax thermal sensor and simple application that read the temperature from it. (Driver for the sensor is not in-tree, it will be delivered in separate PR.)
2. Patch was tested by choosing few combinations of the configuration and verifying which registers are being set in disassembly. Base configuration was also tested by an application that uses two ports.

nsh> tc74_test
tc74_test [4:100]
nsh> Starting TC74 test
Temperature read: 23
Temperature read: 23

[cederom]

Response from kerogit:

the coding style errors in avrdx_lowconsole.c and avrdx_init.c are
fixed. Turns out I forgot to checkpatch some files, sorry about that.
Updated branches are avrdx_twi_rfc1-4 and avrdx_twi_rfc1-2. To be sure, I scanned the series as a whole now and it should hopefully be
everything.

[cederom]

Typos fixed, lets see now :-)