sunxi: change ATF position for H6

H6 has different SRAM A2 address, so the ATF load address is also
different.

Add judgment code to sunxi 64-bit FIT generation script. It will judge
the SoC by the device tree's name.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>