[IA64] perfmon: Remove exit_pfm_fs()

Because it is dead code and not referenced by anybody else (that file cannot
be built modular).

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Stephane Eranian <eranian@hpl.hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/perfmon.c

@@ -1538,13 +1538,6 @@ init_pfm_fs(void)
 	return err;
 }
 
-static void __exit
-exit_pfm_fs(void)
-{
-	unregister_filesystem(&pfm_fs_type);
-	mntput(pfmfs_mnt);
-}
-
 static ssize_t
 pfm_read(struct file *filp, char __user *buf, size_t size, loff_t *ppos)
 {