auxdisplay: hd44780: Fix DT properties to include units of measurement

DT properties specifying physical properties should contain appropriate
suffices indicating the units of measurement.

Hence amend the HD44780 DT bindings to add "chars" suffixes to the
"display-height" and "display-width" properties, and update the driver
to parse them.

Fixes: dd9502a9 ("dt-bindings: auxdisplay: Add bindings for Hitachi HD44780")
Fixes: d47d8836 ("auxdisplay: Add HD44780 Character LCD support")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>