RDMA/ocrdma: Increase the size of STAG array in dev structure to 16K

HW can support 16K STAG entries.  Change this max limit.  Also, move
this array out of ocrdma_dev to reduce the size of this structure.

Signed-off-by: Devesh Sharma <devesh.sharma@emulex.com>
Signed-off-by: Selvin Xavier <selvin.xavier@emulex.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>