selftests: kvm: add amx_test to .gitignore

amx_test's binary should be present in the .gitignore file for the git
to ignore it.

Fixes: bf70636 ("selftest: kvm: Add amx selftest")
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Message-Id: <20220118122053.1941915-1-usama.anjum@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: Muhammad Usama Anjum

tools/testing/selftests/kvm/.gitignore

@@ -8,6 +8,7 @@
 /s390x/memop
 /s390x/resets
 /s390x/sync_regs_test
+/x86_64/amx_test
 /x86_64/cpuid_test
 /x86_64/cr4_cpuid_sync_test
 /x86_64/debug_regs