sunxi: Fix H3 DRAM impedance calibration on rev. A chips

H3 seems to have a silicon bug breaking the impedance calibration.
This is currently worked around in software by multiple steps
combining the results to replace the wrong values.

Revision A chips need a different workaround, which is present in
the vendor bootloader too, but got overlooked in lack of
information and affected boards till now.
This commit adds a simplified version without correction factor,
which would be 1.00 for all known boards anyway.

Signed-off-by: Jens Kuske <jenskuske@gmail.com>
Reviewed-by: Jagan Teki <jteki@openedev.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>