qseecom: Check response result if KMS related scm call returns failure

On the target supporting ARMv8 smc interface, the scm call will return
failure if scm parsing failed or the syscall response result is negative.
Then when qseecom calls __qseecom_generate_and_save_key on a device that
the key is already created, scm call will return failure directly as the
syscall response result value in this case is negative. Thus, generate key
failed and set key will not be called. So, we make changes to check syscall
response results for key management APIs even when scm call return failure.

CRs-Fixed: 723967
Change-Id: Ibade34dfc8ad90b25f2712ed0cc3faae91daab51
Signed-off-by: Zhen Kong <zkong@codeaurora.org>