Fix simple typos

This corrects some trivial errors in ARM docs and comments,

Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting
index fad566b..7685029 100644
--- a/Documentation/arm/Booting
+++ b/Documentation/arm/Booting
@@ -118,7 +118,7 @@
 
 In either case, the following conditions must be met:
 
-- Quiesce all DMA capable devicess so that memory does not get
+- Quiesce all DMA capable devices so that memory does not get
   corrupted by bogus network packets or disk data. This will save
   you many hours of debug.