KVM: selftests: Actually print out magic token in NX hugepages skip message

Pass MAGIC_TOKEN to __TEST_REQUIRE() when printing the help message about
needing to pass a magic value to manually run the NX hugepages test,
otherwise the help message will contain garbage.

  In file included from x86_64/nx_huge_pages_test.c:15:
  x86_64/nx_huge_pages_test.c: In function ‘main’:
  include/test_util.h:40:32: error: format ‘%d’ expects a matching ‘int’ argument [-Werror=format=]
     40 |                 ksft_exit_skip("- " fmt "\n", ##__VA_ARGS__);   \
        |                                ^~~~
  x86_64/nx_huge_pages_test.c:259:9: note: in expansion of macro ‘__TEST_REQUIRE’
    259 |         __TEST_REQUIRE(token == MAGIC_TOKEN,
        |         ^~~~~~~~~~~~~~

Signed-off-by: angquan yu <angquan21@gmail.com>
Link: https://lore.kernel.org/r/20231128221105.63093-1-angquan21@gmail.com
[sean: rewrite shortlog+changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>