KVM: x86: fix empty-body warnings

BugLink: https://bugs.launchpad.net/bugs/1811080

[ Upstream commit 354cb410 ]

We get the following warnings about empty statements when building
with 'W=1':

arch/x86/kvm/lapic.c:632:53: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
arch/x86/kvm/lapic.c:1907:42: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
arch/x86/kvm/lapic.c:1936:65: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]
arch/x86/kvm/lapic.c:1975:44: warning: suggest braces around empty body in an ‘if’ statement [-Wempty-body]

Rework the debug helper macro to get rid of these warnings.
Signed-off-by: Yi Wang <wang.yi59@zte.com.cn>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/x86/kvm/lapic.c

@@ -57,7 +57,7 @@
 #define APIC_BUS_CYCLE_NS 1
 
 /* #define apic_debug(fmt,arg...) printk(KERN_WARNING fmt,##arg) */
-#define apic_debug(fmt, arg...)
+#define apic_debug(fmt, arg...) do {} while (0)
 
 #define APIC_LVT_NUM			6
 /* 14 is the version for Xeon and Pentium 8.4.8*/