msm: secure_buffer: Ensure shared buffers are cache-aligned

Buffers shared with hypervisor might undergo some cache maintenance on
the hypervisor side.  Currently, we're passing a buffer that might not
be cache-aligned (source_vm_list), so when the hypervisor does some
cache maintenance on it they might be corrupting data.  Fix this by
ensuring that all buffers being shared with the hypervisor are
cache-aligned by kmalloc'ing and memcpy'ing the source_vm_list before
sending it across.

Change-Id: I661f8ca852ade159e3432904086b060be8bfb806
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>