[ARM] 3389/1: typo and grammar fix

Patch from Erik Hovland

I found a typo and what seems to be a run-on sentence in
arch/arm/common/dmabounce.c

This patch corrects both.
Signed-off-by: NErik Hovland <erik@hovland.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/common/dmabounce.c

@@ -5,7 +5,7 @@
  *  limited DMA windows. These functions utilize bounce buffers to
  *  copy data to/from buffers located outside the DMA region. This
  *  only works for systems in which DMA memory is at the bottom of
- *  RAM and the remainder of memory is at the top an the DMA memory
+ *  RAM, the remainder of memory is at the top and the DMA memory
  *  can be marked as ZONE_DMA. Anything beyond that such as discontigous
  *  DMA windows will require custom implementations that reserve memory
  *  areas at early bootup.