[nrf fromtree] boards: arm: nrf5340dk_nrf5340: Add SPI to supported peripherals

The target has board configuration for spi_flash sample but bacause
of the lack of SPI mentioned in supported peripherals Twister
is filtering out the target for sample.drivers.spi.flash test.

Signed-off-by: Adam Wojasinski <[email protected]>
(cherry picked from commit 2457a94)

Author: Adam Wojasinski

boards/arm/nrf5340dk_nrf5340/nrf5340dk_nrf5340_cpuapp.yaml

@@ -18,3 +18,4 @@ supported:
   - usb_device
   - netif:openthread
   - gpio
+  - spi

boards/arm/nrf5340dk_nrf5340/nrf5340dk_nrf5340_cpuapp_ns.yaml

@@ -16,3 +16,4 @@ supported:
   - usb_device
   - netif:openthread
   - gpio
+  - spi