alpha: kill off alpha_do_IRQ

Good riddance... Nuke a pile of redundant handlers that the
generic code takes care of as well.

Tested-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Kyle McMartin <kyle@redhat.com>
Signed-off-by: Matt Turner <mattst88@gmail.com>
21 files changed