turn on hashlib for all nrf52840 boards

This turns on hashlib at the port level, but only for nrf52840
boards. There's a comment in mpconfigport.mk suggesting that space
is already tight on nrf52833 boards.

Author: samblenny

ports/nordic/mpconfigport.mk

@@ -63,6 +63,8 @@ CIRCUITPY_MEMORYMAP ?= 1
 CIRCUITPY_RGBMATRIX ?= 1
 CIRCUITPY_FRAMEBUFFERIO ?= 1
 
+CIRCUITPY_HASHLIB ?= 1
+
 CIRCUITPY_COUNTIO ?= 1
 CIRCUITPY_WATCHDOG ?= 1