drivers: auxdisplay: hd44780: rework the initialization procedure

If proper power supply is used to power the hd44780, it initializes
correctly on a reset condition all by itself. However,
if the power supply is below its expectations (e.g. some 3.3V Nucleo
board), it won't initialize properly on its own, and the MCU
has to carry out the initialization as listed in the reference manual.
Since we cannot determine it properly in the runtime,
always carry out the initialization procedure.

Signed-off-by: Jan Kuliga <jtkuliga@gmail.com>