RDMA/hw/qib/qib_mad: Fix a few misspellings and supply missing descriptions

Fixes the following W=1 kernel build warning(s):

 drivers/infiniband/hw/qib/qib_mad.c:896: warning: Function parameter or member 'ppd' not described in 'rm_pkey'
 drivers/infiniband/hw/qib/qib_mad.c:896: warning: Excess function parameter 'dd' description in 'rm_pkey'
 drivers/infiniband/hw/qib/qib_mad.c:926: warning: Function parameter or member 'ppd' not described in 'add_pkey'
 drivers/infiniband/hw/qib/qib_mad.c:926: warning: Excess function parameter 'dd' description in 'add_pkey'
 drivers/infiniband/hw/qib/qib_mad.c:2365: warning: Function parameter or member 'in' not described in 'qib_process_mad'
 drivers/infiniband/hw/qib/qib_mad.c:2365: warning: Function parameter or member 'out' not described in 'qib_process_mad'
 drivers/infiniband/hw/qib/qib_mad.c:2365: warning: Function parameter or member 'out_mad_size' not described in 'qib_process_mad'
 drivers/infiniband/hw/qib/qib_mad.c:2365: warning: Function parameter or member 'out_mad_pkey_index' not described in 'qib_process_mad'
 drivers/infiniband/hw/qib/qib_mad.c:2365: warning: Excess function parameter 'in_mad' description in 'qib_process_mad'
 drivers/infiniband/hw/qib/qib_mad.c:2365: warning: Excess function parameter 'out_mad' description in 'qib_process_mad'

Link: https://lore.kernel.org/r/20210121094519.2044049-10-lee.jones@linaro.org


Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: Mike Marciniszyn <mike.marciniszyn@cornelisnetworks.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-rdma@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>