eal: move OS common config objects

eal: move OS common config objects

Move common functions between Unix and Windows to eal_common_config.c.

Those functions are getter functions for IOVA,
configuration, Multi-process.

Move rte_config, internal_config, early_mem_config and runtime_dir
to be defined in the common file with getter functions.

Refactor the users of the config variables above to use
the getter functions.

Signed-off-by: Tal Shnaiderman <talshn@mellanox.com>