arm: PR 29739 Fix typo where ';' should not have been replaced with '@'

';' does not always indicate the start of a comment, and commit
8cb6e17571f3fb66ccd4fa19f881602542cd06fc incorrectly replaced 3
instances of ';' with '@' in expected diagnostics, leading to tests
failures.

This patch restores the original ';' as needed in these testcases.

Fixes bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29739
3 files changed