vgacon: Fix & cleanup refcounting

The vgacon driver prepares a two element array of uni_pagedir_loc and
uses the second item as its own reference counter for sharing the
uni_pagedir.  And the code assumes blindly that the second item is
available if the assigned vc_uni_pagedir isn't the standard one, which
might be wrong (although currently it's so).

This patch fixes that wrong assumption, and gives a slight cleanup
along with it: namely, instead of array, just give the uni_pagedir_loc
and a separate refcount variable.  It makes the code a bit more
understandable at first glance.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>