rockchip: fit_spl_optee: get text and optee base from build

Instead of hardcode the base address, we can get them from the build
output, eg. get the SYS_TEXT_BASE from .config and get optee base from
DRAM_BASE.
We can use this script for SoCs with DRAM base not from 0x60000000(rk3229
and many other 32bit Rockchip SoCs), eg. rk3288 DRAM base is 0.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>