update submodules to spacecruft mirrors

.gitmodules

@@ -1,32 +1,32 @@
 [submodule "lib/axtls"]
 	path = lib/axtls
-	url = https://github.com/pfalcon/axtls
+	url = https://mirrors.spacecruft.org/pfalcon/axtls
 	branch = micropython
 [submodule "lib/libffi"]
 	path = lib/libffi
-	url = https://github.com/atgreen/libffi
+	url = https://mirrors.spacecruft.org/atgreen/libffi
 [submodule "lib/lwip"]
 	path = lib/lwip
-	url = https://git.savannah.gnu.org/r/lwip.git
+	url = https://mirrors.spacecruft.org/savannah/lwip
 [submodule "lib/berkeley-db-1.xx"]
 	path = lib/berkeley-db-1.xx
-	url = https://github.com/pfalcon/berkeley-db-1.xx
+	url = https://mirrors.spacecruft.org/pfalcon/berkeley-db-1.xx
 [submodule "lib/stm32lib"]
 	path = lib/stm32lib
-	url = https://github.com/micropython/stm32lib
+	url = https://mirrors.spacecruft.org/micropython/stm32lib
 	branch = work-F4-1.13.1+F7-1.5.0+L4-1.3.0
 [submodule "lib/nrfx"]
 	path = lib/nrfx
-	url = https://github.com/NordicSemiconductor/nrfx.git
+	url = https://mirrors.spacecruft.org/NordicSemiconductor/nrfx.git
 [submodule "lib/mbedtls"]
 	path = lib/mbedtls
-	url = https://github.com/ARMmbed/mbedtls.git
+	url = https://mirrors.spacecruft.org/ARMmbed/mbedtls.git
 [submodule "lib/asf4"]
 	path = lib/asf4
-	url = https://github.com/adafruit/asf4
+	url = https://mirrors.spacecruft.org/adafruit/asf4
 [submodule "lib/tinyusb"]
 	path = lib/tinyusb
-	url = https://github.com/hathach/tinyusb
+	url = https://mirrors.spacecruft.org/hathach/tinyusb
 [submodule "lib/mynewt-nimble"]
 	path = lib/mynewt-nimble
-	url = https://github.com/apache/mynewt-nimble.git
+	url = https://mirrors.spacecruft.org/apache/mynewt-nimble.git