lib/mynewt-nimble: Switch to the MicroPython fork of NimBLE.

We will use this fork for adding further features and patches to support
MicroPython.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

.gitmodules

@@ -28,7 +28,7 @@
 	url = https://github.com/hathach/tinyusb
 [submodule "lib/mynewt-nimble"]
 	path = lib/mynewt-nimble
-	url = https://github.com/apache/mynewt-nimble.git
+	url = https://github.com/micropython/mynewt-nimble.git
 [submodule "lib/btstack"]
 	path = lib/btstack
 	url = https://github.com/bluekitchen/btstack.git