RDMA/irdma: Update MAINTAINERS file

Add maintainer entry for irdma driver.

Link: https://lore.kernel.org/r/20210602205138.889-17-shiraz.saleem@intel.com


Signed-off-by: Mustafa Ismail <mustafa.ismail@intel.com>
Signed-off-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>