KVM: selftests: Convert debug-exceptions to printf style GUEST_ASSERT

Convert ARM's debug exceptions  test to use printf-based GUEST_ASSERT().
Opportunistically Use GUEST_ASSERT_EQ() in guest_code_ss() so that the
expected vs. actual values get printed out.

Link: https://lore.kernel.org/r/20230729003643.1053367-12-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>