mem: expose function for physical address use

mem: expose function for physical address use

This function was previously private to the EAL layer.
Other subsystems requires it, such as the PCI bus.

In order not to force other components to include stdbool, which is
incompatible with several NIC drivers, the return type has
been changed from bool to int.

Signed-off-by: Gaetan Rivet <gaetan.rivet@6wind.com>