Fix unused variable compiler warning when built with CONFIG_RAPIDIO_DEBUG
option off.

This patch is applicable to kernel versions starting from v3.2
Signed-off-by: NAlexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>