score: Add missing #include <linux/export.h>

There is no upstream commit for this, as arch/score/kernel/init_task.c
has been replaced by generic code and <linux/export.h> is included
indirectly by arch/score/mm/init.c.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

arch/score/kernel/init_task.c

@@ -23,6 +23,7 @@
 
 #include <linux/init_task.h>
 #include <linux/mqueue.h>
+#include <linux/export.h>
 
 static struct signal_struct init_signals = INIT_SIGNALS(init_signals);
 static struct sighand_struct init_sighand = INIT_SIGHAND(init_sighand);

arch/score/mm/init.c

@@ -34,6 +34,7 @@
 #include <linux/proc_fs.h>
 #include <linux/sched.h>
 #include <linux/initrd.h>
+#include <linux/export.h>
 
 #include <asm/sections.h>
 #include <asm/tlb.h>