bhyve: Fix compile

We need err.h

Fixes:	5cf21e48ccf11 ("bhyve: use a fixed 32 bit BAR base address")
Sponsored by:	Bechoff Automation GmbH & Co. KG

usr.sbin/bhyve/pci_emul.c

@@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/linker_set.h>
 
 #include <ctype.h>
+#include <err.h>
 #include <errno.h>
 #include <pthread.h>
 #include <stdio.h>