x86: move a declaration to header

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/sysemu.h b/sysemu.h
index a96b168..644a97d 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -138,6 +138,7 @@
 #define MAX_NODES 64
 extern int nb_numa_nodes;
 extern uint64_t node_mem[MAX_NODES];
+extern uint64_t node_cpumask[MAX_NODES];
 
 #define MAX_OPTION_ROMS 16
 extern const char *option_rom[MAX_OPTION_ROMS];