refactor(plat/st): remove io_dummy code for OP-TEE
refactor(plat/st): remove io_dummy code for OP-TEE

The io_dummy code and function calls are only used in case BL32 is TF-A
SP_min, and not OP-TEE. This code in bl2_io_storage can then be put under
#ifndef AARCH32_SP_OPTEE.

Signed-off-by: Yann Gautier <e753f6969c288905606e3c07464886d4f1fc1be0@foss.st.com>
Change-Id: I52787a775160b335f97547203f653419621f5147

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware