ila: xlat changes

Change model of xlat to be used only for input where lookup is done on
the locator part of an address (comparing to locator_match as key
in rhashtable). This is needed for checksum neutral translation
which obfuscates the low order 16 bits of the identifier. It also
permits hosts to be in muliple ILA domains (each locator can map
to a different SIR address). A check is also added to disallow
translating non-ILA addresses (check of type in identifier).

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>