Use the nordic_pca10040 BSP

nrf52dk is no longer the correct BSP for the nRF52 board
diff --git a/docs/tutorials/blinky/nRF52.rst b/docs/tutorials/blinky/nRF52.rst
index f8b4ce9..2356b6d 100644
--- a/docs/tutorials/blinky/nRF52.rst
+++ b/docs/tutorials/blinky/nRF52.rst
@@ -75,7 +75,7 @@
 
     $ newt target create nrf52_boot
     $ newt target set nrf52_boot app=@mcuboot/boot/mynewt
-    $ newt target set nrf52_boot bsp=@apache-mynewt-core/hw/bsp/nrf52dk
+    $ newt target set nrf52_boot bsp=@apache-mynewt-core/hw/bsp/nordic_pca10040
     $ newt target set nrf52_boot build_profile=optimized
 
 Run the following ``newt target`` commands to create a target for the
@@ -86,7 +86,7 @@
 
     $ newt target create nrf52_blinky
     $ newt target set nrf52_blinky app=apps/blinky
-    $ newt target set nrf52_blinky bsp=@apache-mynewt-core/hw/bsp/nrf52dk
+    $ newt target set nrf52_blinky bsp=@apache-mynewt-core/hw/bsp/nordic_pca10040
     $ newt target set nrf52_blinky build_profile=debug
 
 You can run the ``newt target show`` command to verify the target
@@ -97,11 +97,11 @@
     $ newt target show
     targets/nrf52_blinky
         app=apps/blinky
-        bsp=@apache-mynewt-core/hw/bsp/nrf52dk
+        bsp=@apache-mynewt-core/hw/bsp/nordic_pca10040
         build_profile=debug
     targets/nrf52_boot
         app=@mcuboot/boot/mynewt
-        bsp=@apache-mynewt-core/hw/bsp/nrf52dk
+        bsp=@apache-mynewt-core/hw/bsp/nordic_pca10040
         build_profile=optimized
 
 Build the Target Executables