tests: exclude arduion_mkrzero from uart_async and spi_loopback tests

uart_async test and spi_loopback test require UART and SPI
with an ASYNC option.
The SAM0 UART/SPI driver requires configuring DMA support.
Arduino MKRZero is not DMA configured like other SAM0 boards.
We exclude it from the tests.

ea36f9b and f4c5bdf already exclude other SAM0 boards from these tests.
Arduino MKRZero also followed these PR policies.

Signed-off-by: TOKITA Hiroshi <tokita.hiroshi@fujitsu.com>
diff --git a/tests/drivers/spi/spi_loopback/testcase.yaml b/tests/drivers/spi/spi_loopback/testcase.yaml
index a69c809..749cebd 100644
--- a/tests/drivers/spi/spi_loopback/testcase.yaml
+++ b/tests/drivers/spi/spi_loopback/testcase.yaml
@@ -2,7 +2,7 @@
   depends_on: spi
   tags: drivers spi
   platform_exclude: seeeduino_xiao serpente arduino_nano_33_iot atsamr21_xpro
-    atsamd21_xpro arduino_zero adafruit_trinket_m0
+    atsamd21_xpro arduino_zero adafruit_trinket_m0 arduino_mkrzero
 tests:
   drivers.spi.loopback:
     harness: ztest
diff --git a/tests/drivers/uart/uart_async_api/testcase.yaml b/tests/drivers/uart/uart_async_api/testcase.yaml
index 9035a11..c7d1a06 100644
--- a/tests/drivers/uart/uart_async_api/testcase.yaml
+++ b/tests/drivers/uart/uart_async_api/testcase.yaml
@@ -2,6 +2,7 @@
   platform_exclude: seeeduino_xiao serpente arduino_nano_33_iot atsamr21_xpro
     adafruit_itsybitsy_m4_express atsame54_xpro atsamd21_xpro adafruit_trinket_m0
     arduino_nano_33_iot arduino_zero atsamd21_xpro adafruit_feather_m0_basic_proto
+    arduino_mkrzero
 
 tests:
   drivers.uart.async_api: