pnp: Add export.h for EXPORT_SYMBOL/THIS_MODULE as required

These macros are no longer in module.h and module.h is no longer
present everywhere.  Call out export.h for the users who are
making use of these macros.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

drivers/pnp/pnpacpi/core.c

@@ -19,6 +19,7 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
+#include <linux/export.h>
 #include <linux/acpi.h>
 #include <linux/pnp.h>
 #include <linux/slab.h>