docs/uos: De-conditionalize statvfs() description.

It's a standard function, and it's already described (in the library
intro) that for any given port, any function may be missing.

docs/library/uos.rst

@@ -61,28 +61,26 @@ Functions
 
    Get the status of a file or directory.
 
-.. only:: port_unix or port_pyboard or port_esp8266
+.. function:: statvfs(path)
 
-    .. function:: statvfs(path)
+   Get the status of a fileystem.
 
-       Get the status of a fileystem.
+   Returns a tuple with the filesystem information in the following order:
 
-       Returns a tuple with the filesystem information in the following order:
+        * ``f_bsize`` -- file system block size
+        * ``f_frsize`` -- fragment size
+        * ``f_blocks`` -- size of fs in f_frsize units
+        * ``f_bfree`` -- number of free blocks
+        * ``f_bavail`` -- number of free blocks for unpriviliged users
+        * ``f_files`` -- number of inodes
+        * ``f_ffree`` -- number of free inodes
+        * ``f_favail`` -- number of free inodes for unpriviliged users
+        * ``f_flag`` -- mount flags
+        * ``f_namemax`` -- maximum filename length
 
-            * ``f_bsize`` -- file system block size
-            * ``f_frsize`` -- fragment size
-            * ``f_blocks`` -- size of fs in f_frsize units
-            * ``f_bfree`` -- number of free blocks
-            * ``f_bavail`` -- number of free blocks for unpriviliged users
-            * ``f_files`` -- number of inodes
-            * ``f_ffree`` -- number of free inodes
-            * ``f_favail`` -- number of free inodes for unpriviliged users
-            * ``f_flag`` -- mount flags
-            * ``f_namemax`` -- maximum filename length
-
-       Parameters related to inodes: ``f_files``, ``f_ffree``, ``f_avail``
-       and the ``f_flags`` parameter may return ``0`` as they can be unavailable
-       in a port-specific implementation.
+   Parameters related to inodes: ``f_files``, ``f_ffree``, ``f_avail``
+   and the ``f_flags`` parameter may return ``0`` as they can be unavailable
+   in a port-specific implementation.
 
 .. function:: sync()