Revert "nfs: ignore SB_RDONLY when mounting nfs"

This reverts commit 52cb7f8.

Silently ignoring the "ro" and "rw" mount options causes user confusion,
and regressions.

Reported-by: Alkis Georgopoulos<alkisg@gmail.com>
Cc: Li Lingfeng <lilingfeng3@huawei.com>
Fixes: 52cb7f8 ("nfs: ignore SB_RDONLY when mounting nfs")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Author: Trond Myklebust

fs/nfs/internal.h

@@ -13,7 +13,7 @@
 #include <linux/nfslocalio.h>
 #include <linux/wait_bit.h>
 
-#define NFS_SB_MASK (SB_NOSUID|SB_NODEV|SB_NOEXEC|SB_SYNCHRONOUS)
+#define NFS_SB_MASK (SB_RDONLY|SB_NOSUID|SB_NODEV|SB_NOEXEC|SB_SYNCHRONOUS)
 
 extern const struct export_operations nfs_export_ops;