x86/vPIC: correct vpic_domain()

Make it use its parameter in both places.

Fixes: 00a70f44a6 ("[HVM] Update VPIC device model for new interrupt delivery code")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>

xen/arch/x86/hvm/vpic.c

@@ -35,7 +35,7 @@
 #include <asm/hvm/save.h>
 
 #define vpic_domain(v) (container_of((v), struct domain, \
-                        arch.hvm.vpic[!vpic->is_master]))
+                                     arch.hvm.vpic[!(v)->is_master]))
 #define __vpic_lock(v) &container_of((v), struct hvm_domain, \
                                         vpic[!(v)->is_master])->irq_lock
 #define vpic_lock(v)   spin_lock(__vpic_lock(v))