SPM: Rename local handle pointer variable name

Rename the connection handle struct pointer name to
"handle" or "conn_handle" to indicate it is a handle
pointer.

The API "spm_get_handle_by_signal()" is used by IPC
backend only, fix the missing backend config macro of it.

Signed-off-by: Mingyang Sun <mingyang.sun@arm.com>
Change-Id: I705f6c4c63452d39d7bc142da90043b85a82854c
9 files changed