The lkey_table_size driver specific parameter value is used before its
value is sanity checked and restricted to RVT_MAX_LKEY_TABLE_BITS.

This causes a vmalloc allocation failure for large values. Fix this
by moving the value check before the first usage of the value.
Reviewed-by: NDennis Dalessandro <dennis.dalessandro@intel.com>
Reviewed-by: NMike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: NJubin John <jubin.john@intel.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>