bus/fslmc: restrict address translation to PA mode

bus/fslmc: restrict address translation to PA mode

The address translation support for PA->VA is required only in
case of PA mode operation of DPDK. This was causing warning to
be reported on running any DPAA2 application in VA mode:

    Add: Incorrect entry for PA->VA Table(xxxxxxxxxx)
    Add: Lowest address: xxxxxxxxxxxx

This was caused by call to update the DPAAX table when VA mode
was enabled, in which case the VA==IOVA address.

Signed-off-by: Shreyansh Jain <shreyansh.jain@nxp.com>
Reviewed-by: Sachin Saxena <sachin.saxena@nxp.com>