qed: Read device port count from the shmem

Read port count from the shared memory instead of driver deriving this
value. This change simplifies the driver implementation and also avoids
any dependencies for finding the port-count.

Signed-off-by: Sudarsana Reddy Kalluru <skalluru@marvell.com>
Signed-off-by: Michal Kalderon <mkalderon@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>