octeontx2-pf: disable preemption while using per_cpu pointer

commit 6c6acfa9e815030c366666b8106885ec2abcba14 from
git@git.assembla.com:cavium/WindRiver.linux.git

Current code uses per_cpu pointer to get the lmtst_id mapped to the core
on which aura_free() is executed. Using per_cpu pointer without
preemption disable will cause mismatch between lmtst_id and core on
which pointer gets freed. Hence disable preemption around aura_free.

Change-Id: Iff94d64b5f1fec481267cf67dc3d6519c63913e4
Signed-off-by: Geetha sowjanya <gakula@marvell.com>
Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
[RQ: Drop the parts which have been already applied.]
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>