Remove references to bundled mbedtls library to use the one from inputs.

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1e27d21..f0eb1a5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -85,13 +85,6 @@ endif()
 
 set(USE_STATIC_MBEDTLS_LIBRARY ON)
 set(USE_SHARED_MBEDTLS_LIBRARY OFF)
-add_subdirectory("lib/mbedtls" EXCLUDE_FROM_ALL)
-
-# Compile the mbedtls library as a static with position independent code,
-# because we need it for both a shared and static library
-set_property(TARGET mbedtls PROPERTY POSITION_INDEPENDENT_CODE ON)
-set_property(TARGET mbedcrypto PROPERTY POSITION_INDEPENDENT_CODE ON)
-set_property(TARGET mbedx509 PROPERTY POSITION_INDEPENDENT_CODE ON)
 
 add_subdirectory(src)