qseecom: allocate sglistinfo buffer for kernel clients

To support whitelist feature, sglistinfo table should also
be allocated from qseecom kernel APIs used by kernel client.
Besides, initialize sg in __qseecom_update_cmd_buf_64 to
address a static analysis warning.

Change-Id: I1f1967fd9e95444cca728f09e3e8f4914b2abb95
Signed-off-by: Zhen Kong <zkong@codeaurora.org>