arm64: gitignore: ignore relacheck

Add the generated executable for relacheck to the list of ignored files.
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://lore.kernel.org/r/20240222210441.33142-1-brgl@bgdev.plSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/pi/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
+
+relacheck