perf tools: Add all shellcheck_log to gitignore

Instead of adding specific shellcheck_log files to the gitignore, add
all of them to prevent these files from cluttering the git status.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20241104-shellcheck_gitignore-v1-1-ffc179f57dc9@rivosinc.com


Signed-off-by: Namhyung Kim <namhyung@kernel.org>