Revert "zephyr:boards nrf52840_pca10056 rename to nrf52840dk_nrf52840"

This reverts commit fefdea20d2697e2098c5b5cdd646fcef7ecc3590.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
diff --git a/boot/zephyr/sample.yaml b/boot/zephyr/sample.yaml
index 548b30b..62518c1 100644
--- a/boot/zephyr/sample.yaml
+++ b/boot/zephyr/sample.yaml
@@ -5,16 +5,16 @@
 tests:
   sample.bootloader.mcuboot:
     tags: bootloader_mcuboot
-    platform_whitelist: nrf52840dk_nrf52840 frdm_k64f
+    platform_whitelist: nrf52840_pca10056 frdm_k64f
   sample.bootloader.mcuboot.serial_recovery:
     extra_args: OVERLAY_CONFIG=serial_recovery.conf
-    platform_whitelist:  nrf52840dk_nrf52840
+    platform_whitelist:  nrf52840_pca10056
     tags: bootloader_mcuboot
   sample.bootloader.mcuboot.usb_cdc_acm_recovery:
     tags: bootloader_mcuboot
     platform_whitelist:  nrf52840_pca10059
   sample.bootloader.mcuboot.usb_cdc_acm_recovery_log:
     extra_args: OVERLAY_CONFIG=./usb_cdc_acm_log_recovery.conf
-      DTC_OVERLAY=./boards/nrf52840_big.overlay
-    platform_whitelist:  nrf52840dk_nrf52840
+      DTC_OVERLAY=./boards/nrf52840_pca10056_big.overlay
+    platform_whitelist:  nrf52840_pca10056
     tags: bootloader_mcuboot