rapidio: improve a size determination in five functions

Replace the specification of data structures by pointer dereferences as
the parameter for the operator "sizeof" to make the corresponding size
determination a bit safer according to the Linux coding style
convention.

This issue was detected by using the Coccinelle software.

Link: http://lkml.kernel.org/r/495f571c-fb4d-b1d5-a6e5-494f2c537a8d@users.sourceforge.net


Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Acked-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>