zynqmp: Generate u-boot.its also with TEE dynamically

zynqmp: Generate u-boot.its also with TEE dynamically

The first change is to trying to find out TF-A load address based on
reading elf file. Expectation is that bl31.bin is in the same folder as
bl31.elf. It brings new flexibility to place TF-A to any address (DDR
included).

And also enable TEE generation also with TEE configuration.
Expecation is the same as above that tee.bin and tee.elf are in the same
folder.

User has to just define link to BL31/BL32 binary files and the rest should
be handled by the script.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>