[tip:ia64/urgent] Fix sn_force_interrupt_flag no defination issue

["Alex,Shi" <alex.shi@intel.com>]

sn_force_interrupt_flag was removed in 39-rc1 patch. But it still be
used in arch/ia64/sn/kernel/sn2/sn_proc_fs.c. that make compilation
failed: 
arch/ia64/sn/built-in.o: In function `sn_force_interrupt_show':
sn_proc_fs.c:(.text+0xd281): undefined reference to `sn_force_interrupt_flag'
sn_proc_fs.c:(.text+0xd2a0): undefined reference to `sn_force_interrupt_flag'
A quick fix for this.

Signed-off-by: Alex Shi <alex.shi@intel.com>
---
 arch/ia64/sn/kernel/sn2/sn_proc_fs.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/ia64/sn/kernel/sn2/sn_proc_fs.c b/arch/ia64/sn/kernel/sn2/sn_proc_fs.c
index c76d8dc..ce3215d 100644
--- a/arch/ia64/sn/kernel/sn2/sn_proc_fs.c
+++ b/arch/ia64/sn/kernel/sn2/sn_proc_fs.c
@@ -51,7 +51,7 @@ static int licenseID_open(struct inode *inode, struct file *file)
  * the bridge chip.  The hardware will then send an interrupt message if the
  * interrupt line is active.  This mimics a level sensitive interrupt.
  */
-extern int sn_force_interrupt_flag;
+int sn_force_interrupt_flag;
 
 static int sn_force_interrupt_show(struct seq_file *s, void *p)
 {