Revert "hvc_console: display printk messages on console."

This reverts commit 36116245.

It causes an infinite loop when booting Linux under Xen, as so:

  [    2.382984] console [hvc0] enabled
  [    2.382984] console [hvc0] enabled
  [    2.382984] console [hvc0] enabled
  ...

as reported by Konrad Rzeszutek Wilk.  And Rusty reports the same for
lguest.  He goes on to say:

   "This is not a concurrency problem: the issue seems to be that
    calling register_console() twice on the same struct console is a bad
    idea."

and Greg says he'll fix it up properly at some point later. Revert for now.

Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reported-by: Rusty Russell <rusty@ozlabs.org>
Requested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Miche Baker-Harvey <miche@google.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>