escc: implement hard reset as described in the datasheet

escc: implement hard reset as described in the datasheet

The hardware reset differs from a device reset in that it only changes the contents
of specific registers. Remove the code that resets all the registers to zero during
hardware reset and implement the default values using the existing soft reset code
with the additional changes listed in the table in the "Z85C30 Reset" section.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20210903113223.19551-7-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>