rockchip: Move TEXT_BASE to 8 MiB offset from start of DRAM

rockchip: Move TEXT_BASE to 8 MiB offset from start of DRAM

Drop SoC specific TEXT_BASE and use a common TEXT_BASE for all SoCs.

Move the common TEXT_BASE to 8 MiB offset from start of DRAM to help
support RAM boot from maskrom introduced in next patch.

RAM boot from maskrom mode will expect the FIT payload to be located at
2 MiB offset from start or DRAM.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Tested-by: Arnaud Patard <arnaud.patard@collabora.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>