auxdisplay: hd44780: Fix memory leak on ->remove()

We have to free on ->remove() the allocated resources on ->probe().

Fixes: d47d8836 ("auxdisplay: Add HD44780 Character LCD support")
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>