attiny841: Fix TWI:TWSCRB:TWAA enumerated values

Actually this is just a single bit so 2-bit enum values don't make
sense.  Newer svd2rust versions check whether enum values fit which
caught this error.  Fix it.

all: Drop unnecessary access mode patches

Due to a change in atdf2svd [1], all these access mode patches are no
longer required - they are now translated correctly from the vendor
source file.

Drop all patches which no longer change the output (the code before and
after this change is equivalent when using the new atdf2svd).

[1]: https://github.com/Rahix/atdf2svd/commit/a189276b3540b647fab832946edf0acf39730a0e

Add attiny841 and attiny861