RDMA/irdma: Fix the type used to declare a bitmap

'bitmapbuf' is really used as a bitmap, so it should be defined as a
'unsigned long *' to be more consistent with the bitmap API.

Link: https://lore.kernel.org/r/574b773fe7ced0cc87f1e1832350b38374815bd4.1638647428.git.christophe.jaillet@wanadoo.fr


Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>