Allow users to create bigger MRs. Remove the check that prevented creating
MRs with number of pages more than 512.

Link: https://lore.kernel.org/r/1610012608-14528-3-git-send-email-selvin.xavier@broadcom.comSigned-off-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>