auxdisplay: lcd2s: Use proper API to free the instance of charlcd object

auxdisplay: lcd2s: Use proper API to free the instance of charlcd object

BugLink: https://bugs.launchpad.net/bugs/1964361
commit 9ed331f8a0fb674f4f06edf05a1687bf755af27b upstream.

While it might work, the current approach is fragile in a few ways:
- whenever members in the structure are shuffled, the pointer will be wrong
- the resource freeing may include more than covered by kfree()

Fix this by using charlcd_free() call instead of kfree().

Fixes: 8c9108d014c5 ("auxdisplay: add a driver for lcd2s character display")
Cc: Lars Poeschel <poeschel@lemonage.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>