hvc_console: display printk messages on console.

printk only works for "registered consoles."  Currently, the hvc_console
code calls register_console() from hvc_instantiate(), but that's only
used in the early console case.  In hvc_alloc(), register_console() was
not called.

Add a call to register_console() in hvc_alloc(), set up the index in
the hvc_console, and set up the necessary vtermnos[] and cons_op[]
entries so that printk functions work.

Signed-off-by: Miche Baker-Harvey <miche@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>