Build: Add Cmake argument MBEDCRYPTO_GIT_REMOTE

To be able to redirect the fetching of mbedtls. This makes it possible
to have a local clone that TFM fetches from, and the correct version
and patches are always used, as opposed to using MBEDCRYPTO_PATH where
you must always manually keep the clone in sync with the current version
and patches.

Change-Id: I8c316ecdb13b0deff80605f4b3f0acca8f5d2ed5
Signed-off-by: Øyvind Rønningstad <oyvind.ronningstad@nordicsemi.no>
diff --git a/lib/ext/mbedcrypto/CMakeLists.txt b/lib/ext/mbedcrypto/CMakeLists.txt
index 79adce1..9a0340a 100644
--- a/lib/ext/mbedcrypto/CMakeLists.txt
+++ b/lib/ext/mbedcrypto/CMakeLists.txt
@@ -19,7 +19,7 @@
 
     if (PATCH_FILES)
         FetchContent_Declare(mbedcrypto
-            GIT_REPOSITORY https://github.com/ARMmbed/mbedtls.git
+            GIT_REPOSITORY ${MBEDCRYPTO_GIT_REMOTE}
             GIT_TAG ${MBEDCRYPTO_VERSION}
             GIT_SHALLOW TRUE
             GIT_PROGRESS TRUE
@@ -28,7 +28,7 @@
         )
     else()
         FetchContent_Declare(mbedcrypto
-            GIT_REPOSITORY https://github.com/ARMmbed/mbedtls.git
+            GIT_REPOSITORY ${MBEDCRYPTO_GIT_REMOTE}
             GIT_TAG ${MBEDCRYPTO_VERSION}
             GIT_SHALLOW TRUE
             GIT_PROGRESS TRUE