fs/inode: using rwsem lock as inode_lock to avoid deadlock

Example:
When executing "df -h" on Core A to view mount information, this
process will traverse inode nodes, thereby holding the inode_lock.
Since the inode type of the mount point may be rpmsgfs, it will fetch statfs
information from another Core B.

Meanwhile, rcS on Core B needs to obtain file information from Core A,
which will be achieved by fetching stat information through rpmsgfs.
When this message arrives at Core A, a deadlock can occur between Core A's
rptun ap and nsh task.

However, both of these places involve read operations only, thus a reader-writer lock
can be utilized to prevent such a deadlock.

Signed-off-by: dongjiuzhu1 <dongjiuzhu1@xiaomi.com>

fs/mount/fs_umount2.c

@@ -110,12 +110,7 @@ int nx_umount2(FAR const char *target, unsigned int flags)
 
   /* Hold the semaphore through the unbind logic */
 
-  ret = inode_lock();
-  if (ret < 0)
-    {
-      goto errout_with_mountpt;
-    }
-
+  inode_lock();
   ret = mountpt_inode->u.i_mops->unbind(mountpt_inode->i_private,
                                        &blkdrvr_inode, flags);
   if (ret < 0)