chore: move mbedtls into contrib

Align with other submodules so they all live in the same subdirectory.

Change-Id: I784d69f4473fa06fea7e0c1ec0d53abf2c8ca12f
Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
diff --git a/.gitmodules b/.gitmodules
index 844ca3c..a5a55ef 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,5 +1,5 @@
 [submodule "ext/mbedtls"]
-	path = ext/mbedtls
+	path = contrib/mbedtls
 	url = https://github.com/Mbed-TLS/mbedtls.git
 [submodule "libtl"]
 	path = contrib/libtl
diff --git a/ext/mbedtls b/contrib/mbedtls
similarity index 100%
rename from ext/mbedtls
rename to contrib/mbedtls
diff --git a/lib/ext_mbedtls/mbedtls.mk b/lib/ext_mbedtls/mbedtls.mk
index 74ab284..bc2e261 100644
--- a/lib/ext_mbedtls/mbedtls.mk
+++ b/lib/ext_mbedtls/mbedtls.mk
@@ -4,7 +4,7 @@
 # SPDX-License-Identifier: BSD-3-Clause
 #
 
-MBEDTLS_DIR ?= ext/mbedtls
+MBEDTLS_DIR ?= contrib/mbedtls
 ifeq (${MBEDTLS_DIR},)
 $(error Error: MBEDTLS_DIR not set)
 endif