octeontx2-pf: Fix coverity and klockwork issues in octeon PF driver

Fix unintended sign extension and klockwork issues. These are not real
issue but for sanity checks.

Signed-off-by: Ratheesh Kannoth <rkannoth@marvell.com>
Signed-off-by: Suman Ghosh <sumang@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>