Backport "[AVR] Fix parsing & emitting relative jumps" (try 2)

[aykevl]

Let's try this again, now with both commits needed for a fix (that doesn't result in a test failure).

/cherry-pick 86a60e7
/cherry-pick a3816b5

[llvmbot]

/pull-request #107082

[aykevl]

/cherry-pick 86a60e7 a3816b5

This was meant to include both commits. Maybe this syntax will work?

[aykevl]

Looks like this one does indeed work! The llvmbot has updated #107082 to include both commits.