remoteproc: mtk_scp: Only populate devices for SCP cores

remoteproc: mtk_scp: Only populate devices for SCP cores

When multi-core SCP support was added, the driver was made to populate
platform devices for all the sub-nodes. This ended up adding platform
devices for the rpmsg sub-nodes as well, which never actually get used,
since rpmsg devices are registered through the rpmsg interface.

Limit of_platform_populate() to just populating the SCP cores with a
compatible string match list.

Fixes: 1fdbf0cdde98 ("remoteproc: mediatek: Probe SCP cluster on multi-core SCP")
Cc: Tinghan Shen <tinghan.shen@mediatek.com>
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20241211072009.120511-1-wenst@chromium.org
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>