IB/hfi1: Remove wrapper function in mmu_rb

Wrapper functions were used to call the same function
mmu_notifier_mem_invalidate for 2 callbacks in
mmu_notifier.
The commit 7def96f0 ("IB/hfi1: update to new mmu_notifier semantic")
removed the invalidate_page callback.
Therefore, the wrapper function is no longer needed.

Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Reviewed-by: Alex Estrin <alex.estrin@intel.com>
Signed-off-by: Kamenee Arumugam <kamenee.arumugam@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>