optee: Add CONFIG_OPTEE_LOAD_ADDR

optee: Add CONFIG_OPTEE_LOAD_ADDR

CONFIG_OPTEE_LOAD_ADDR is used to tell u-boot where to load the OPTEE
binary into memory prior to handing off control to OPTEE.

We need to pull this value out of u-boot in order to produce an IMX IVT/CSF
signed pair for the purposes of secure boot. The best way to do that is to
have CONFIG_OPTEE_LOAD_ADDR appear in u-boot.cfg.

Adding new CONFIG entires to u-boot should be kconfig driven so this patch
does just that.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Ryan Harkin <ryan.harkin@linaro.org>