KVM: selftests: Add printf attribute to _no_printf()

Annotate the KVM selftests' _no_printf() with the printf format attribute
so that the compiler can help check parameters provided to pr_debug() and
pr_info() irrespective of DEBUG and QUIET being defined.

[reinette: move attribute right after storage class, rework changelog]

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/r/898ec01580f6f4af5655805863239d6dce0d3fb3.1734128510.git.reinette.chatre@intel.com


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