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/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt
index a87d4a8..12a008a 100644
--- a/Documentation/networking/packet_mmap.txt
+++ b/Documentation/networking/packet_mmap.txt
@@ -278,7 +278,7 @@
 All memory allocations are not freed until the socket is closed. The memory 
 allocations are done with GFP_KERNEL priority, this basically means that 
 the allocation can wait and swap other process' memory in order to allocate 
-the nececessary memory, so normally limits can be reached.
+the necessary memory, so normally limits can be reached.
 
  Other constraints
 -------------------