64bit addresses not supported for MSI

[bjorn3]

For 64bit MSI capabilities, the high half of the address is left untouched by set_message_info. set_message_info will need to be changed to accept a 64bit address and write the upper half for 64bit MSI capabilities too.

[bjorn3]

Also set_message_info should probably document the address alignment requirement when using multiple message support.

[bjorn3]

And a minor thing: set_message_mask has access as first argument rather than as last like all other methods.