szedata2: support link state operations

szedata2: support link state operations

Mmap PCI resource file and add inline functions for reading from and
writing to PCI resource address space.
Add description of IBUF and OBUF address space.
Add configuration option for setting which firmware type will be used.
Right address space values for IBUFs and OBUFs offsets are used
according to configuration option CONFIG_RTE_LIBRTE_PMD_SZEDATA2_AS.
Setting link up/down and getting info about link status is done through
mmapped PCI resource address space.

Signed-off-by: Matej Vido <vido@cesnet.cz>