lib: arm_ffa: Add support for MSG_SEND_DIRECT_REQ2 UUID demuxing This change allows UUID specific handlers to be installed for MSG_SEND_DIRECT_REQ2. Bug: 380065728 Change-Id: I54a95e8893da49c831c8c400f802550673af28d2 Signed-off-by: Jay Monkman <jmonkman@google.com>