`checkpatch.pl` requires that dts sources are indented with tabs,
fix all the spaces that slipped in while checkpatch wasn't watching.
Signed-off-by: Jordan Yates <jordan@embeint.com>
Add a MSPI controller API test and run on native_sim board.
The API implementation within mspi_emul.c is the test target.
The stub device emulator is added for convenience to test controllers.
Signed-off-by: Swift Tian <swift.tian@ambiq.com>
