fusion: fix excess parameter kernel-doc warning

Fix kernel-doc excess parameter warning:

Warning(..//drivers/message/fusion/mptbase.c:1411): Excess function parameter 'prod_name' description in 'mpt_get_product_name'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Ewan D. Milne <emilne@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>