Having a transfer more than 32 bits is not all that unlikely.  Remove
the annotation.

The unlikely in the IRQ handler can't gain us much.  It's not in a
loop, so at most it would save 1 instruction per IRQ, which isn't
much.  In fact on the compiler I tested it produced the exact same
code.  Remove it too.
Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>