docs/vm: rename documentation files to .rst

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index e96adcb..f53e506 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -584,7 +584,7 @@
 	  Say Y to support efficient handling of discontiguous physical memory,
 	  for architectures which are either NUMA (Non-Uniform Memory Access)
 	  or have huge holes in the physical address space for other reasons.
-	  See <file:Documentation/vm/numa> for more.
+	  See <file:Documentation/vm/numa.rst> for more.
 
 source "mm/Kconfig"