IMA: convert i_readcount to atomic

Convert the inode's i_readcount from an unsigned int to atomic.

Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: Eric Paris <eparis@redhat.com>

include/linux/fs.h

@@ -794,8 +794,7 @@ struct inode {
 #endif
 
 #ifdef CONFIG_IMA
-	/* protected by i_lock */
-	unsigned int		i_readcount; /* struct files open RO */
+	atomic_t		i_readcount; /* struct files open RO */
 #endif
 	atomic_t		i_writecount;
 #ifdef CONFIG_SECURITY