tty: vt: change consw::con_set_origin() return type

tty: vt: change consw::con_set_origin() return type

The return value of consw::con_set_origin() is only true/false, meaining
if vc->vc_origin is set to vc->vc_screenbuf or not.

So switch the type and returned values accordingly.

And document the hook.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: linux-fbdev@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Tested-by: Helge Deller <deller@gmx.de> # parisc STI console
Link: https://lore.kernel.org/r/20240122110401.7289-39-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>