Fix simple typos

This corrects some trivial errors in ARM docs and comments,

Signed-off-by: Adrian Bunk <bunk@stusta.de>

Documentation/arm/Booting

@@ -118,7 +118,7 @@ to store page tables.  The recommended placement is 32KiB into RAM.
 
 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.
 

Documentation/arm/README

@@ -89,7 +89,7 @@ Modules
   Although modularisation is supported (and required for the FP emulator),
   each module on an ARM2/ARM250/ARM3 machine when is loaded will take
   memory up to the next 32k boundary due to the size of the pages.
-  Therefore, modularisation on these machines really worth it?
+  Therefore, is modularisation on these machines really worth it?
 
   However, ARM6 and up machines allow modules to take multiples of 4k, and
   as such Acorn RiscPCs and other architectures using these processors can

Documentation/arm/Setup

@@ -58,7 +58,7 @@ below:
  video_y
 
    This describes the character position of cursor on VGA console, and
-   is otherwise unused. (should not used for other console types, and
+   is otherwise unused. (should not be used for other console types, and
    should not be used for other purposes).
 
  memc_control_reg