This commit excludes thingy53_nrf5340_cpuapp_ns platform from building
wpanusb and wpan_serial samples. The platform doesn't support TF-M yet
and therefore the build is bound to fail.
Due to limitations of the filter functionality, a more generic approach
where _ns platforms without TF-M support would be excluded from the
build, for example:
filter: dt_chosen_enabled("zephyr,ieee802154") and
CONFIG_NRF_SOC_SECURE_SUPPORTED
doesn't properly filter out the needed platforms. As a result,
platform_exclude syntax is used to specifically exclude the platform.
Signed-off-by: Jędrzej Ciupis <jedrzej.ciupis@nordicsemi.no>