mbedtls: move source modification to patch

Patch the mbedtls source instead of modifying the compile-targets
in the prepare buildstep within OpenWrt.

Signed-off-by: David Bauer <mail@david-bauer.net>

package/libs/mbedtls/patches/101-remove-test.patch

@@ -0,0 +1,15 @@
+--- a/programs/CMakeLists.txt
++++ b/programs/CMakeLists.txt
+@@ -1,12 +1,8 @@
+ add_subdirectory(aes)
+-if (NOT WIN32)
+-    add_subdirectory(fuzz)
+-endif()
+ add_subdirectory(hash)
+ add_subdirectory(pkey)
+ add_subdirectory(psa)
+ add_subdirectory(random)
+ add_subdirectory(ssl)
+-add_subdirectory(test)
+ add_subdirectory(util)
+ add_subdirectory(x509)