Fix typos in Documentation/: 'N'-'P'

This patch fixes typos in various Documentation txts. The patch addresses
some words starting with the letters 'N'-'P'.

Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/Documentation/block/barrier.txt b/Documentation/block/barrier.txt
index de3d88e..a272c3d 100644
--- a/Documentation/block/barrier.txt
+++ b/Documentation/block/barrier.txt
@@ -42,7 +42,7 @@
 of ii.  Just keeping issue order suffices.  Ancient SCSI
 controllers/drives and IDE drives are in this category.
 
-2. Forced flushing to physcial medium
+2. Forced flushing to physical medium
 
 Again, if you're not gonna do synchronization with disk drives (dang,
 it sounds even more appealing now!), the reason you use I/O barriers