spcom: add ION buffer support

Add new spcom API to allow user to send request/response with ION buffer.
The spcom kernel driver modify the request/response by replacing the
user ION buffer virtual address with the buffer physical address.
spcom also provide API to lock/unlock the ION buffer to avoid the SP side
using an ION buffer that was free when HLOS App crashed.

CRs-Fixed: 986215
Change-Id: I5dca692cd3c4fac63be5ec73f89e6c39a593a50b
Signed-off-by: Amir Samuelov <amirs@codeaurora.org>