[ARM] 3632/1: iwmmxt: fix up argument comment for iwmmxt_task_restore()

Patch from Lennert Buytenhek

Commit d6551e88 forgot to update the
description of what goes into r2 when calling iwmmxt_task_restore().

Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>