firmware: qcom_scm: Use qtee_shmbridge if available

Secure world imposed that buffer exchanges between secure and non-secure
worlds be allocated from qtee_shmbridge, so add a function to allocate
buffer space using shmbridge for extra arguments. Change helps in
dealing with early scm calls when the driver is not initialized.

Change-Id: I270b4aef9d33ec6d7ea0897ddcc0944ac9e1833f
Signed-off-by: Elliot Berman <eberman@codeaurora.org>