[SPARC64] sunhv: Bug fixes.

Add udelay to polling console write loop, and increment
the loop limit.

Name the device "ttyHV" and pass that to add_preferred_console()
when we're using hypervisor console.

Kill sunhv_console_setup(), it's empty.

Handle the case where we don't want to use hypervisor console.
(ie. we have a head attached to a sun4v machine)

Signed-off-by: David S. Miller <davem@davemloft.net>