Move crypto hardware acceleration configuration

The crypto hardware acceleration might require defining a lot of mbed
TLS specific macros. Enumerating all of them in `targets.json` creates
too much noise, therefore we move it into a target specific mbed TLS
header.

The target with crypto hardware acceleration has to
        - indicate its capability in `targets.json` by adding "CRYPTO"
          to the "device_has" section
        - has to define his crypto hardware acceleration related macros
          in an `mbedtls_device.h` header
        - place the `mbedtls_device.h` file in the
          `features/mbedtls/targets/TARGET_XXXX`
          directory specific to the target

Author: yanesca

features/mbedtls/importer/Makefile

@@ -93,7 +93,6 @@ clean:
 	rm -f $(TARGET_PREFIX)apache-2.0.txt
 	rm -f $(TARGET_PREFIX)VERSION.txt
 	rm -f $(TARGET_PREFIX)AUTHORS.txt
-	rm -rf $(TARGET_PREFIX)/targets
 	rm -rf $(TARGET_SRC)
 	rm -rf $(TARGET_INC)
 	rm -rf $(MBED_TLS_DIR)

features/mbedtls/platform/inc/platform_mbed.h

@@ -20,3 +20,7 @@
 #if defined(DEVICE_TRNG)
 #define MBEDTLS_ENTROPY_HARDWARE_ALT
 #endif
+
+#if defined(DEVICE_CRYPTO)
+#include "mbedtls_device.h"
+#endif