KVM: selftests: Convert ARM's hypercalls test to printf style GUEST_ASSERT

Convert ARM's hypercalls test to use printf-based GUEST_ASSERT().
Opportunistically use GUEST_FAIL() to complain about an unexpected stage.

Link: https://lore.kernel.org/r/20230729003643.1053367-13-seanjc@google.com


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