lguest: add export.h to lguest files for THIS_MODULE/EXPORT_SYMBOL

We need this in advance of the module.h cleanup, or we'll
get compile errors like this:

CC drivers/lguest/lguest_device.o
drivers/lguest/lguest_device.c: In function ‘lguest_devices_init’:
drivers/lguest/lguest_device.c:490: error: ‘THIS_MODULE’ undeclared (first use in this function)

Signed-off-by: Paul Gortmaker <[e-mail]>

arch/x86/lguest/boot.c

···
 #include <linux/lguest_launcher.h>
 #include <linux/virtio_console.h>
 #include <linux/pm.h>
+#include <linux/export.h>
 #include <asm/apic.h>
 #include <asm/lguest.h>
 #include <asm/paravirt.h>

drivers/lguest/lguest_device.c

···
 #include <linux/interrupt.h>
 #include <linux/virtio_ring.h>
 #include <linux/err.h>
+#include <linux/export.h>
 #include <linux/slab.h>
 #include <asm/io.h>
 #include <asm/paravirt.h>

drivers/lguest/lguest_user.c

···
 #include <linux/eventfd.h>
 #include <linux/file.h>
 #include <linux/slab.h>
+#include <linux/export.h>
 #include "lg.h"
 
 /*L:056