[llvm] [AVR] Fix parsing & emitting relative jumps (PR #106722)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `lld-x86_64-ubuntu-fast` running on `as-builder-4` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/33/builds/2119

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'lld :: ELF/avr-reloc.s' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 2: /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llvm-mc -filetype=obj -triple=avr -mcpu=atmega328p /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/lld/test/ELF/avr-reloc.s -o /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/tools/lld/test/ELF/Output/avr-reloc.s.tmp0.o
+ /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/bin/llvm-mc -filetype=obj -triple=avr -mcpu=atmega328p /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/lld/test/ELF/avr-reloc.s -o /home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/build/tools/lld/test/ELF/Output/avr-reloc.s.tmp0.o
/home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/lld/test/ELF/avr-reloc.s:99:1: error: out of range branch target (expected an integer in the range -4096 to 4095)
rjmp 1f + 4094  $ 1:  ; R_AVR_13_PCREL
^
/home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/lld/test/ELF/avr-reloc.s:101:1: error: out of range branch target (expected an integer in the range -4096 to 4095)
rjmp 1f + 4096  $ 1:  ; R_AVR_13_PCREL (overflow)
^
/home/buildbot/worker/as-builder-4/ramdisk/lld-x86_64/llvm-project/lld/test/ELF/avr-reloc.s:103:1: error: out of range branch target (expected an integer in the range -128 to 127)
breq 1f + 126   $ 1:  ; R_AVR_7_PCREL
^

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/106722