IB/core: Add mitigation for Spectre V1

IB/core: Add mitigation for Spectre V1

[ Upstream commit 61f259821dd3306e49b7d42a3f90fb5a4ff3351b ]

Some processors may mispredict an array bounds check and
speculatively access memory that they should not. With
a user supplied array index we like to play things safe
by masking the value with the array size before it is
used as an index.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20190731043957.GA1600@agluck-desk2.amr.corp.intel.com
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>