fix(direct message request): incorrect response for illegal transition

FF-A v1.1 EAC0 spec states that partition manager must return DENIED
as the error code when an illegal transition is attempted by a vCPU.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: Ibb86cc4e688c9f64d83a776dddb4434c741d268f
1 file changed