`assert(e)` was used in place of `if (e) ERROR()` when sec_protect()
was ported from hikey fork so the logic should have been reversed.

Fixes: 3d5d9f5a ("hikey: configure the top 16MB of DRAM as secure")
Fixes: 52988b38 ("hikey: configure 4 MB of secure DRAM for OP-TEE
Secure Data Path")
Signed-off-by: Victor Chong <victor.chong@linaro.org>
Tested-by: Victor Chong <victor.chong@linaro.org>