machine/microbit-v2: add initial support based on work done by @alankrantas thank you!

Signed-off-by: deadprogram <ron@hybridgroup.com>

targets/microbit-v2.json

@@ -0,0 +1,8 @@
+{
+	"inherits": ["nrf52833"],
+	"build-tags": ["microbit_v2"],
+	"flash-method": "msd",
+	"openocd-interface": "cmsis-dap",
+	"msd-volume-name": "MICROBIT",
+	"msd-firmware-name": "firmware.hex"
+}

targets/nrf52833.json

@@ -0,0 +1,17 @@
+{
+	"inherits": ["cortex-m4"],
+	"build-tags": ["nrf52833", "nrf"],
+	"cflags": [
+		"-Qunused-arguments",
+		"-DNRF52833_XXAA",
+		"-I{root}/lib/CMSIS/CMSIS/Include",
+		"-I{root}/lib/nrfx/mdk"
+	],
+	"linkerscript": "targets/nrf52833.ld",
+	"extra-files": [
+		"lib/nrfx/mdk/system_nrf52833.c",
+		"src/device/nrf/nrf52833.s"
+	],
+	"openocd-transport": "swd",
+	"openocd-target": "nrf52"
+}

targets/nrf52833.ld

@@ -0,0 +1,10 @@
+
+MEMORY
+{
+    FLASH_TEXT (rw) : ORIGIN = 0x00000000, LENGTH = 0x80000
+    RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 0x20000
+}
+
+_stack_size = 4K;
+
+INCLUDE "targets/arm.ld"