[CIFS] reopen file via newer posix open protocol operation if available

If the network connection crashes, and we have to reopen files, preferentially
use the newer cifs posix open protocol operation if the server supports it.

Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 596fc86..a069e7b 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -92,6 +92,9 @@
 extern __le64 cnvrtDosCifsTm(__u16 date, __u16 time);
 extern struct timespec cnvrtDosUnixTm(__u16 date, __u16 time);
 
+extern int cifs_posix_open(char *full_path, struct inode **pinode,
+			   struct super_block *sb, int mode, int oflags,
+			   int *poplock, __u16 *pnetfid, int xid);
 extern void posix_fill_in_inode(struct inode *tmp_inode,
 				FILE_UNIX_BASIC_INFO *pData, int isNewInode);
 extern struct inode *cifs_new_inode(struct super_block *sb, __u64 *inum);