optee: Add optee_image_get_load_addr()

optee: Add optee_image_get_load_addr()

This patch adds optee_image_get_load_addr() a helper function used to
calculate the load-address of an OPTEE image based on the lower
entry-point address given in the OPTEE header.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc: Harinarayan Bhatta <harinarayan@ti.com>
Cc: Andrew F. Davis <afd@ti.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Kever Yang <kever.yang@rock-chips.com>
Cc: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Cc: Peng Fan <peng.fan@nxp.com>
Tested-by: Peng Fan <peng.fan@nxp.com>