[PATCH] docs/mm: Physical Memory: correct spelling in reference to CONFIG_PAGE_EXTENSION

[Lukas Bulwahn <lukas.bulwahn@gmail.com>]

Commit 5d8c5e430a63 ("docs/mm: Physical Memory: add structure, introduction
and nodes description") slips in a minor spelling mistake for the config
PAGE_EXTENSION.

Correct the config name in the physical-memory documentation.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
---
 Documentation/mm/physical_memory.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/mm/physical_memory.rst b/Documentation/mm/physical_memory.rst
index 3f3c02aa6e6e..f9d7ea4b9dca 100644
--- a/Documentation/mm/physical_memory.rst
+++ b/Documentation/mm/physical_memory.rst
@@ -210,7 +210,7 @@ General
 ``node_page_ext``
   For UMA systems that use FLATMEM memory model the 0's node
   ``node_page_ext`` is array of extensions of struct pages. Available only
-  in the kernels built with ``CONFIG_PAGE_EXTENTION`` enabled.
+  in the kernels built with ``CONFIG_PAGE_EXTENSION`` enabled.
 
 ``node_start_pfn``
   The page frame number of the starting page frame in this node.
-- 
2.17.1