drv: add header files

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>

drivers/fmc/fmc-core.c

@@ -8,6 +8,10 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/module.h>
 #include "fmc-internal.h"
 #include "fmc-compat.h"