optee: Add optee_verify_bootm_image()

This patch adds optee_verify_bootm_image() which will be subsequently used
to verify the parameters encoded in the OPTEE header match the memory
allocated to the OPTEE region, OPTEE header magic and version prior to
handing off control to the OPTEE image.

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>