auxdisplay: charlcd: replace last device specific stuff

These are the last bits left in charlcd.c that are device specific and
they are removed now.
In detail this is:
* bwidth, which is the width of the display buffer per line. This is
  replaced by width of the display.
* hwidth, which is the size of the display buffer as a whole. This is
  replaced by looping all chars of a line by all lines.
* the hd44780_common header include can go away.

Reviewed-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>