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>

Author: yamahata

tools/testing/selftests/kvm/include/test_util.h

@@ -22,7 +22,7 @@
 
 #define msecs_to_usecs(msec)    ((msec) * 1000ULL)
 
-static inline int _no_printf(const char *format, ...) { return 0; }
+static inline __printf(1, 2) int _no_printf(const char *format, ...) { return 0; }
 
 #ifdef DEBUG
 #define pr_debug(...) printf(__VA_ARGS__)