ARM: io: fix comment grammar

Signed-off-by: Andrew F. Davis <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

arch/arm/include/asm/io.h

···
  * These perform PCI memory accesses via an ioremap region.  They don't
  * take an address as such, but a cookie.
  *
- * Again, this are defined to perform little endian accesses.  See the
+ * Again, these are defined to perform little endian accesses.  See the
  * IO port primitives for more information.
  */
 #ifndef readl