fix(plat/mediatek/mt8183): fix out-of-bound access
fix(plat/mediatek/mt8183): fix out-of-bound access

Fix coverity checks which is found on:
https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/1806/comment/eaec126f_af5eb624/

Change-Id: I9405f7f67aa4115c1a7b8b4623b6b0830e62f814
Signed-off-by: Tinghan Shen <c9ff063c8de5b2a8e3ffacf80169ee51e722b470@mediatek.com>

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