fix(handoff): fix register convention in opteed

The commit with Change-Id:Ie417e054a7a4c192024a2679419e99efeded1705
updated the register convention r1/x1 values but missing necessary
changes in BL31.
As a result, a system panic observed during setup for BL32 when
TRANSFER_LIST is enabled due to unexpected arguments.
This patch is to fix this issue for optee.

Change-Id: I13e116e7cb5a7d89fafc11d20295cffbf24793ab
Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
1 file changed