Switch the SoC device tree to define a single entry per SERCOM instead
of one per mode.
Define a Device Tree binding for the SAM0 SPI and use it instead of
Kconfig for enabling / disabaling instances
Switch the Arduino Zero, Adafruit Feather M0 Basic Proto, and
Trinket M0 to use the new defintion.
Add the APA102 LED that's on the Trinket as a test.
Signed-off-by: Michael Hope <mlhx@google.com>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>