stm class: Propagate source type to protocols

Pass stm source type via stm_write() to allow different handling on
protocol level.

The measure above should allow protocol level encoder to differentiate
and accordingly pack the messages. As an example SyS-T might get use of
ftrace message ID's and instead of applying regular header, pack them
as SyS-T catalog or SyS-T Structured Binary Data message to allow proper
decoding on the other side.

Signed-off-by: Mikhail Lappo <miklelappo@gmail.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240429130119.1518073-4-alexander.shishkin@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>